CN100352767C - Calcium sulphate-based compositions and methods of making same - Google Patents
Calcium sulphate-based compositions and methods of making same Download PDFInfo
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- CN100352767C CN100352767C CNB2004800121481A CN200480012148A CN100352767C CN 100352767 C CN100352767 C CN 100352767C CN B2004800121481 A CNB2004800121481 A CN B2004800121481A CN 200480012148 A CN200480012148 A CN 200480012148A CN 100352767 C CN100352767 C CN 100352767C
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Abstract
Disclosed is an improved alpha calcium sulfate hemihydrate. Methods of producing an improved powdered calcium sulfate hemihydrate (CaSO4.1/2H2O) [alpha-type] compound are disclosed, at least one method including forming calcium sulfate dihydrate (CaSO4<.>2H2O) into a briquette under high pressure, calcining the briquette to transform the calcium sulfate dihydrate to calcium sulfate hemihydrate [alpha-type], drying the calcium sulfate hemihydrate [alpha-type] briquette, and optionally grinding the briquette. Also disclosed are methods of producing an improved gypsum plaster including producing the disclosed powdered calcium sulfate hemihydrate [alpha-type] and mixing the powdered calcium sulfate hemihydrate [alpha-type] with water.
Description
Technical field
This disclosure generally is about based on gypsum with based on the composition and the manufacture method thereof of calcium sulfate, and more particularly about architectural grade gypsum model composition and manufacture method thereof.
Background technology
In multiple industry, particularly use composition and compound in the building industry based on gypsum and calcium sulfate.For example, gypsum plaster is widely used in (as automatic leveller) in the building products, for example is used for pouring into a mould floor technology and mending mortar.Utilize heating from gypsum or calcium sulfate dihydrate (CaSO
42H
2O) drive away moisture in to form calcium sulfate hemihydrate (CaSO
41/2H
2O), it generally can make gypsum plaster used in these products.Gypsum plaster is also referred to as the plaster of Paris or plaster.
Can make and carry out dehydration or calcining in many ways.For example can by flash drying at high temperature, boiling in cauldron, heating in smelting furnace or rotary kiln, use steam or in aqeous suspension boiling carry out calcining.Many these different technology can produce the plaster with extensive composition and characteristic, but generally form two types: alpha-hemihydrate type and β-semihydrate type.By the amount of water these two types are distinguished from each other, water is that to make the pourable mortar with the Powdered semihydrate of smooth grinding necessary, during for alpha-hemihydrate, every 100g plaster need be less than the water of about 50ml, and when being β-semihydrate, need to surpass substantially the water of this amount, common every 100g semihydrate plaster need be greater than 70ml water.This water yield is called as water requirement.
Become known for making the method for the α calcium sulfate hemihydrate that is fit to material of construction, the gypsum of its humidity that is obtained by desulfurization from the power station exhaust gas discharged of burning brown coal segmentation and making, particularly the gypsum (being called desulfurated plaster or DSG) that is obtained by waste-gas desulfurization in the wet waste-gas desulfurization unit makes.This method is by in the presence of saturated vapor, and recrystallize transforms the calcium sulfate dihydrate that is contained among the DSG and carries out.
Become known for calcium sulfate dihydrate is converted into the different methods of α calcium sulfate hemihydrate.A kind of described method that is used for making alpha-hemihydrate from the plaster of paris is described during the 301st page of " this industrial chemistry encyclopaedia of Liv Ullmann " (Ullmans Encyclopedia of Industrial Chemistry) the 12nd phase in 1976 to some extent.In this method, with the calcium sulfate dihydrate sheet, i.e. the gypsum plate of natural generation is put into autoclave and in the presence of saturated vapor, under the temperature of 275 , is translated into the alpha-hemihydrate sheet at 266 in autoclave.This alpha-hemihydrate product is transformed back on the temperature (-113 ) of calcium sulfate dihydrate dry and pulverize approximately to be used for further use at semihydrate.
More particularly, the gypsum that will from natural sediment, remove be decomposed into 150 to 300 millimeters (mm) granularity, be packed in the basket and put into the autoclave of basket.With autoclave directly or indirectly with the steam heating of 266 to 275 .According to the saturated vapor curve, the control heating is so that set up the pressure of 4 to 5 crust (bar) (0.4 to 0.5MPa) in about 4 hours.By this method calcium sulfate dihydrate is converted into alpha-hemihydrate and spends at least 6 hours usually.Then autoclave is turned.Introduce alpha-semi water plaster stone in the kiln in the basket and dry and smooth grinding subsequently under the standard pressure of about 221 .At the surf zone of material piece, the alpha-hemihydrate crystallization of sharp outline is with the shape growth of similar pin sample.Fig. 1 shows scanning electronic microscope (SEM) Photomicrograph by the pin sample crystallization example of the alpha-hemihydrate that this method obtained.
The additive metered supply that can control the pH value with being used for and be used to change the crystallization pattern is to autoclave and obtain to have the alpha-hemihydrate product of various characteristics.Yet in this currently known methods, expensive purifying step is very bothersome.In this method, significantly the appearance of alpha-hemihydrate crystalline is mostly is for chance, and the control method of the relevant crystallization pattern and the crystal surface microtexture that forms is not provided.
In order to attempt head it off, the method described in No. the 5th, 015,449, the United States Patent (USP) of Koslowski of for example giving is between 0.1 to 14N/mm
2(MPa) make moist fine particulate shape gypsum (calcium sulfate dihydrate) form molding under the pressure.Koslowski claims when passing through greater than 16N/mm
2The following extruding calcium sulfate dihydrate and when forming molding of pressure, " one of process obtains molded or formed body, but its not autoclavable and form fragmentation or fracture and during autoclaving, be damaged ".7, the 41-45 are capable in the Koslowski special column.
What the molded gypsum body of institute's revealing method had that the volume of voids of cumulative volume 15 to 60 volume % and cumulative volume be higher than 5 volume % among the Koslowski contains the air void volume.When starting material are when wetting, remaining hole has been full of water.Then molding is put into autoclave.By being controlled at, process temperature in the scope of 230 and 356 , reaches the crystallization pattern of regulating crystalline growth and alpha-hemihydrate by the atmospheric pressure of the process in the autoclave.After recrystallize transforms, molding is removed from autoclave and be delivered for use.
Produce the crystallization of prism-shaped α calcium sulfate hemihydrate by this method, shown this crystalline SEM Photomicrograph among Fig. 2.The calcination time that is used to produce these crystalline methods approximately be every batch 4 to 7 hours.With regard to production efficiency, this long period time makes this method difficult and expensive.
Thereby, in this industry, exist up to now to address the aforementioned drawbacks and insufficient needs.
Summary of the invention
The product that the embodiment of this disclosure provides a kind of calcium sulfate hemihydrate [α-type] (" alpha-hemihydrate ") with crystal habit of improvement, make the method for alpha-hemihydrate and use the alpha-hemihydrate that disclosed to make.
The concise and to the point description, the embodiment of described method that generation has an alpha-hemihydrate of improvement crystal habit comprises under high pressure makes calcium sulfate dihydrate form a briquet, calcines described briquet so that calcium sulfate dihydrate is converted into alpha-hemihydrate, dry this briquet and grinds this briquet according to circumstances.In an embodiment of the alpha-hemihydrate that is disclosed, described alpha-hemihydrate crystallization is grown to form haptophore together, compare with the volume of voids of the alpha-hemihydrate of being made by the briquet that forms under the pressure that is less than or equal to 14 megapascal (MPa)s (Mpa), it has volume of voids between the one-tenth cluster that reduces substantially.The mixture that comprises alpha-hemihydrate and water with an embodiment of the product of announcement alpha-hemihydrate manufacturing.
Description of drawings
According to following accompanying drawing, can better understand many aspects of this disclosure.Component in the accompanying drawing is not necessarily to scale.In addition, same reference number is indicated the corresponding section that spreads all over some views.
Fig. 1 describes prior art calcium sulfate hemihydrate [α-type] (" alpha-hemihydrate ") crystalline scanning electronic microscope (SEM) Photomicrograph that forms by calcined calcium sulfate hemihydrate dihydrate stone.
Fig. 2 describes the prior art calcium sulfate hemihydrate crystalline SEM Photomicrograph that forms through molded calcium sulfate dihydrate by calcining.
Fig. 3 describes the improvement alpha-hemihydrate crystalline SEM Photomicrograph that disclosed.
Fig. 4 represents to produce the water content and the pressure range of the briquet that discloses, and the quality of the briquet that produces.
The calcining speed of exemplary briquet of Fig. 5 graphic representation and piece.
Fig. 6 graphic representation uses that art methods carries out run through calcined blocks inside by the number turnover of gypsum to semihydrate, prove the calcination time that the art methods needs are grown relatively.
Fig. 7 A-7D is the calcination time that shows through increasing, the crystalline growth microgram of Kerr-McGee gypsum.
The autoclave temperature that Fig. 8 graphic representation pilot-plant test is compared with the laboratory calcining.
Fig. 9 graphic representation has used an embodiment of institute's revealing method to make the calcining speed in briquet and two kinds of different crown fillers of incinerating source.
An embodiment of institute's revealing method is used in Figure 10 graphic representation, and the process variable of pressure is to the influence of gypsum to the calcining speed of semihydrate.
Figure 11 is the synoptic diagram that describes laboratory scale conventional grinding plant design in detail.
The water requirement of the exemplary semihydrate material that the embodiment of Figure 12 graphic representation by institute's revealing method prepares from different gypsum source.
The embodiment of Figure 13 graphic representation by institute's revealing method, pressure boost when making briquet and the water requirement of the various semihydrate materials that prepare.
Figure 14 A-14I is the Photomicrograph of the crystalline texture of the exemplary semihydrate product of explanation.Notice that Figure 14 E takes under different enlargement ratios, and Figure 14 I is a ratio.
The embodiment of Figure 15 graphic representation by institute's revealing method increases water content and the water requirement of the exemplary semihydrate material for preparing when making briquet.
The embodiment of Figure 16 graphic representation by institute's revealing method, used gypsum adds exemplary additive or directly additive is added in the briquet and the water requirement of the exemplary semihydrate material of preparation when making briquet.
Figure 17 is that explanation is used an embodiment of institute's revealing method and the bar graph of the exemplary void content through the calcining briquet for preparing.
Figure 18 is that explanation is used an embodiment of institute's revealing method and the bar graph of the exemplary void content without the calcining briquet for preparing.
Figure 19 graphic representation time of drying for the embodiment by institute's revealing method make exemplary through calcining but be the influence of the dryness factor of wet big briquet.
Figure 20 graphic representation under 194 drying/pulverizing for the embodiment by institute's revealing method make exemplary through calcining but be the influence of the dryness factor of wet big briquet.
The compressive strength of the exemplary product that Figure 21 graphic extension is made by alpha-hemihydrate is to the percentile dependency of flying dust replace sand.
Figure 22 A and 22B are the graphic extensions for the granularity and the distribution of shapes data of exemplary starting material gypsum that computer produces.
Figure 23 A-23C is the graphic extension for granularity and distribution of shapes data after the embodiment processing of gypsum revealing method being subjected to of Fig. 9 that computer produces.
Embodiment
Such as before affirmation, gypsum plaster or calcium sulfate hemihydrate (CaSO
41/2H
2O) [alpha-hemihydrate] (hereinafter " alpha-hemihydrate ") and manufacture method thereof have long calcination time, and therefore expensive, and are not always to be enough to produce consistent alpha-hemihydrate.For attempting to solve some these problems, developed the method that other is used to make alpha-hemihydrate, it comprises expensive additive and/or complex installation and operating process, often causes long calcination time but still can not produce the alpha-hemihydrate with best crystalline texture.What therefore, need is can reach fast easily to produce to have the alpha-hemihydrate of best crystalline texture to be used to produce firm gypsum plaster product.Disclosed is a kind of alpha-hemihydrate product of improvement, it forms even more ideally, with subsequently grinding and dry after produce the plaster of high strength, low water demand.In addition, the manufacture method of the alpha-hemihydrate of this improvement is easier and more effective than the method for other known generation alpha-hemihydrate.
Now referring to Fig. 3, its demonstration be improvement alpha-hemihydrate crystalline scanning electronic microscope (SEM) Photomicrograph that is disclosed.The monocrystalline of known alpha-hemihydrate has the median size (Fig. 2) of about 20 microns (μ m).From Fig. 3 the ratio of Photomicrograph as can be seen, the alpha-hemihydrate haptophore of improvement or the median size of group are about 100 μ m.From the alpha-hemihydrate crystalline of Fig. 1 and 2 relatively as seen, the improvement alpha-hemihydrate cocooning tool of Fig. 3 has littler volume of voids, and the alpha-hemihydrate haptophore that is disclosed is than the pin sample of Fig. 1 and 2 or the cylindricality crystallization is bigger and more approaching bulk.The crystalline texture of this " more approaching bulk " causes the improved characteristics of material, for example water requirement of Jian Shaoing.More approaching blocky crystallization causes more effective packing volume, and its minimizing is used to produce the water yield of the mortar of wanting.Except shape facility, granularity is also influential to the water requirement characteristic.The extensive size-grade distribution of spherical or block crystalline provides the charging efficiency of maximum and minimum water requirement.
An one exemplary embodiment that is used to make the method for alpha-hemihydrate comprises under high pressure makes calcium sulfate dihydrate (CaSO
42H
2O) (hereinafter " dihydrate ") forms a briquet, the described briquet of calcining so that calcium sulfate dihydrate is converted into the α calcium sulfate hemihydrate, dry this briquet also grinds this briquet according to circumstances.The dihydrate that is used to form briquet comprises the plaster of paris that comes from tellurian ore deposit and stone quarry, and the by product gypsum that comes from the number of chemical process.Some examples of these chemical processes comprise the production of waste-gas desulfurization, titanium dioxide, based on the production of phosphatic fertilizer, the neutralization of waste sulfuric acid stream that comes from chemical process or the production of organic acid and salt (for example citric acid, Citrate trianion etc.) thereof.The recirculation gypsum that comes from the gypsum product also is suitable for this method.The special example of dihydrate material includes, but is not limited to Lambton desulfurated plaster (LDSG), Kerr-McGee gypsum (KMG), comes near the plaster of paris of Ontario, Canada Du Lubai, comes from Dodge, U.S. Iowa neighbouring plaster of paris (" Fort Dodge terra alba ") and recirculation plasterboard core.
With instructed in the prior art opposite, the present inventor is unexpectedly definite: under high pressure form the dihydrate briquet and can obtain can not rupturing or the destructive briquet in calcination process.It should be noted that the combination that forms pressure and free water content for some, can be observed some less breaking, but this breaks and neither destroys briquet and also do not hinder its use.For each research material, can reach in order to produce do not rupture the formation high pressure of briquet and the optimal combination of free water content.In an example, can form briquet down at the pressure that almost can't work up to briquetting press greater than the pressure of about 14 megapascal (MPa)s (MPa) (about usually 320MPa).For example, when with less relatively water or when not adding water and compressing dihydrate, under high pressure (320MPa according to appointment), briquetting press begins to send the ear-piercing body of high-decibel level, even if make the operator use the ear protection, can not stand.For the dihydrate that adds water, under high pressure (320MPa according to appointment), briquet begins to cling or be attached on the machine part.Thereby can form the residing upper limit of pressure of briquet mainly is the function of the operational limits of briquetting press.In theory, the comparable current pressure limitation of studying of progress of the briquetting technique of the bigger pressure of following permission is even more ideal.
In another example, can under about pressure of 50 to 300Mpa, form briquet.In another example, determined that formed briquet presents useful characteristic under 100 to 200Mpa pressure.Fig. 4 shows that detailed description can form the synoptic diagram in residing pressure of briquet and moisture zone.These process variables directly help the abundant ability that produces and control without the calcined gypsum product, are called " quality " of the briquet that forms herein.The quality of this briquet also is the raw-material function of used gypsum.
There are some factors can influence the easy degree of briquet manufacturing and the total intensity of briquet.Its transportation of the intensity effect of briquet, transmission etc. and the ability that is not damaged simultaneously.Description of the Prior Art a kind of method, be lower than the piece that makes gypsum form size about 10cm * 20cm * 20cm under the pressure of 14Mpa thus.For example, used briquet can be in size variation in the method disclosed herein, for example the cubic inch from about 0.125 (" less " type) to 125 (" bigger " types).In another example, briquet is about 1 to 27 cubic inch.Definite, in another example, about 1 to 8 cubic inch briquet presents beneficial characteristics.For example, briquet can be about 2 square inches thick 1 inch of bottom surface.Term used herein " briquet " refers to the block dihydrate material of the tight moulding that forms under pressure.For example, brick shape piece can (for example) be the pillow sample shape of the charcoal brick of charcoal barbecue grill (as be used for), stone buttress sample, plate sample, cylindrical, flat board etc.
Generally has physical bond water in 15 to 21 weight % scopes at the dihydrate briquet that forms under the high pressure that is disclosed.This is for 75 to 100% pure gypsum.The preferably pure gypsum of 85-100% or 17 to 21% physical bond water, and best be 93 to 100% pure gypsum or 19.5 to 21% physical bond water.
Except physical bond water, and be different from physical bond water, briquet also can be included as and be beneficial to processing (for example in the processing of briquet or during forming lubricated briquet and thereby increase the compressibility of dihydrate material) and add free water in the briquet to.In addition, the free water of adding in the briquet can help out in recrystallization process by assist thermal conduction and/or recrystallize during the calcining briquet.Use special charging mechanism and production-scale briquetting equipment can make anhydrous briquet or moisture scope only greater than 0 weight %, 12 weight % at the most.In an example, free water is about 1 to 5 weight % of briquet.Definite, the free water content of about 2 to 3 weight % obtains useful result at the institute's revealing method that is used for making the semihydrate that discloses.
In the temperature range of about 248 to 284 , the dihydrate briquet that calcining is disclosed.The dihydrate briquet that under high pressure forms is to calcine than traditional speed faster rate of finishing gypsum calcination as mentioned above.For example, as seen from Figure 5, when using KMG, during being less than about 1 hour calcining, institute's revealing method has been finished the conversion from the dihydrate to the alpha-hemihydrate substantially, and only finishes about 40% according to the relatively large of prior art in about 3 hours time range.
Fig. 6 further specifies, if checked the plaster block described in the prior art after the improper 6 hours calcination time at 3 hours, for example by gypsum in the transformation of semihydrate, the dehydration at plaster block edge is finished substantially.Yet, the not calcining fully of inch sample that degree of depth part obtains from surface to 1/2, and almost not calcining of the sample of obtaining from plaster block inside.Notice that " finishing substantially " used herein refers to that about 93% briquet is converted into alpha-hemihydrate, about 3 are left dihydrate to 4%.Remaining 3 to 4% can be (for example) various dirts.
Can determine the per-cent composition of dihydrate, semihydrate, free water and other material by following gypsum facies analysis program.The empty receptacle of weighing also writes down the identifier based on container.About 4 to 6 gram samples are added in this container and (use mortar and pestle smooth grinding in advance).The weight of record mortar and container is also placed a night in air (being preferably the relative humidity of 60-80%).Under about 113 with dry about 2 hours of sample and weigh.Careful add about 20ml distilled water, guaranteed all powder moistening.Be positioned over it on counter and covered about 2 hours.It is placed a night and writes down weight in the baking oven of about 113 .Under about 572 , sample was heated about 2 hours.Place on the coolship sample and covering.One is cooled to available hand touch promptly weighs once more.Calculate % water, % dehydrated gyp-(III), % dihydrate, % semihydrate and other weight %.
Can carry out microscopy shown in Fig. 7 A-7D to briquet after the calcination process.Carry out with incinerating, the briquet of being made by KMG as shown in Figure 4 is broken and checked to determine crystallite size and shape.After about 15 minutes (Fig. 7 B), the crystallization of briquet intermediary look to calcine before initial briquet similar, but evidence suggests and begin to form the little white gypsum crystallization of monoblock clearly.During by about 45 minutes (Fig. 7 C), may be grown to for the bigger clear crystallization of semihydrate and can represent nearly all material within the vision.After about 6 hours (Fig. 7 D), overall structure looks similar, the big slightly sign of crystallization when showing some semihydrate crystallizations than 45 minutes simultaneously.
Can be by to the selection of dry autoclave used in the type of briquet size, the moisture content that forms the residing pressure of briquet, briquet, institute's calcined gypsum, the calcining and the optimization calcination time.Make briquets by two kinds of general different technology, a kind of is good " laboratory " method of control process parameters, and second method is used commercially available briquetting equipment.
Laboratory technique is as follows: parent material is laid on the plane domain (for example on bake plate or the clean table top) and uses rolling pin that bigger material block is pulverized.Use the spray bottle interpolation water yield as calculated uniformly, and the thorough mixing material.With the material that will measure put into have cup-shaped form the surface cylindrical mould.To have the block up hydropress (the Forney Inc.Hermitage that comes from Pennsylvania, America) of telltale (the Admet Inc.ofNorwood that comes from Massachusetts, United States) of slip gauge the material in the mould is exerted pressure.Calculating be used to reach the weight of the briquet pressure of wanting (must know the area of piston), and pressurize up to instrument measurement to this quantity.Piston is regained and briquet is removed from mould.Briquet is stored in the reclosable bag to be used for autoclave processing subsequently.Used autoclave is a Magnaclave Model MC autoclave, by the Pelton ﹠amp of North Carolina; Crane ofCharlotte makes.After autoclave is handled, with briquet under 194 in Yamato DKN600 constant temperature oven (from the Yamato ScientificAmerica Inc. in Zhi Bao city, New York, United States Oran (Orangeburg)) dried overnight.The briquet that produces by this program is called as " laboratory briquet " hereinafter.
Briquetting is as follows finishes " interim test scale ": by the K R Komarek Briquetting Research of U.S. Alabama An Nisidun, Ltd. forms briquet on B-400A type that Komarek makes or B-220QC type roller press.The material that comes from hopper is provided on the gap of the roll that is driven by variable speed drive units by horizontal screw.Utilize paddle stirrer that material is stirred in the horizontal screw at opening for feed place.Then with material compacting between two rolls, these two rolls are by on the shaft end of cantilever support outside bearing support.The adjustment type hydraulic efficiency system provides the power that roll is clamped together entirely.The isolating power of roll that makes that material produced of compacting equates on amplitude in this power and the roll seam.Inflatable pressure accumulator in the hydraulic efficiency system is as the rigidity of pressure accumlator and pressure accumulator precharge pressure decision hydraulic efficiency system.According to the previous laboratory scale program of explaining some briquets that made by the Komarek briquetting press are carried out autoclave processing and dry.The briquet that produces by this program is called as " interim test briquet " hereinafter.
Except that laboratory scale autoclaving, use the production-scale autoclave that comes from North Carolina BondtechInc.of Salisbury to carry out the autoclaving test of big interim test scale.Equipment used has one about 5 feet high 10 feet long, and one cylindrical pressure chamber is at one end arranged.By one independently boiler provide steam to the pressure chamber, supply with some other unit in the factory, thereby give than this required more turnout in special single unit.If need, also this pressurized vessel of vacuum available system equipment makes it possible to find time to come from most of air of pressure chamber.
By previous described interim test method on a small scale, under the pressure of the moisture of about 1-2% and about 178MPa, obtain the briquet that 1.6 * 1.0 * 0.5 inch size and about 22g weigh and prepare the gypsum briquet.With in these a large amount of briquets (about 1717 pounds) wire basket that to be loaded into two high about 3 feet bottom surfaces be 4 square feet in size and be placed in the pressure chamber.Thermopair is embedded into 12 inches places of briquet base portion, in order to the temperature of briquet during the monitoring calcining.The pressure chamber is vacuumized and then use the live steam pressurization make room temp reach about 270 .This interim test scale autoclave incinerating temperature curve is compared in Fig. 8 demonstration with the temperature curve that laboratory scale calcining is obtained.As seen, the device of interim test scale provides closely similar temperature profile from temperature curve, but after reaching set temperature value soon, have a more tangible temperature to plunge, it continues about 30 minutes.Bound by theory can not infer that it is the result of heat absorption calcination process that temperature plunges, and it comes from the heat of live steam by briquet consumption and reduces temperature and produce.
After 140 minutes, open with at the outside of wire basket placement 6 forced ventilation space heaters (each electric capacity of 1500 watts), be used for the drying of the hot briquet of assisting pressure container with the autoclave venting and with door.When container cools off, can obtain considerable heat from 6000 pounds containers itself, but in drying process except these portable space well heaters, do not apply other heat.In drying process, the door of container is opened 1.5 to 3.5 inches, make water vapor select and minimize cooling by the briquet due to the ambient air.
5.5 after hour, the water that wire basket is removed from the chamber and weighs and lost from the gypsum briquet to determine.Because still for what wet, the free water in the briquet can be used for making semihydrate to transform back into gypsum to briquet, but the loss of gross weight still is certain.With regard to 1717 pounds initial gypsum weight of gypsum briquet, between this calcining and dry epoch, lose 182 pounds water.For 95% the pure gypsum briquet that contains 1% water, the theory loss that gypsum changes semihydrate into is 270.7 pounds.Till when finishing, the briquet drying about 67% when finishing.
The exemplary briquet that taking-up is used to analyze has confirmed this result.Do not analyze briquet immediately and therefore make its cooling, make any free water that semihydrate is transformed back into gypsum.Briquet on the briquet base surface of the most close door is 94.22% semihydrate, 2.73% gypsum and 0.39% water by analysis.Briquet on the top surface at second basket rear portion is 89.07% semihydrate, 4.04% gypsum and 0.39% free water by analysis, and it shows that some remainder water change some semihydrates into gypsum.Away from door, the gypsum that is embedded in 8 inches places, basket middle distance surface is very moist, and only is 34.4% semihydrate, 53.1% gypsum and about 1.3% free water by analysis.
As shown in Figure 9, the calcining of speed that different gypsum materials can be different, it is slow slightly that the calcining speed ratio that comes from the KMG of titanium dioxide production comes from the speed of LDSG of waste-gas cleaning.
The research calcining temperature is for the influence of calcining speed, and determines all at 240 and 270 , is higher than that samples tested all shows similar degree of calcination and all fully calcined under 30 minutes the calcination time.Under less calcination time, calcining temperature that may be higher can increase calcining speed.
As shown in Figure 10, under 30 minutes the calcination time, the pressure that forms along with briquet increases, and calcining speed also increases.
The use that shows additive also can have influence on calcining speed.Additive is generally used for producing the α semihydrate via wet autoclave method, in order to the crystal form of regulating final product and reduce its water requirement.The accelerator that additive can be speed such as vitriolate of tartar in order to increase recrystallization process speed and such as the crystal habit conditioning agent of succsinic acid (or corresponding salt) in order to crystal form is changed into the form that is easier to processing from the pin sample.Data declaration crystal habit conditioning agent shown in the following table 1 can slow to transformation efficiency to a certain degree.Under these conditions, decide the quickening or the calcining speed that slows down that its use can be more or less on the vitriolate of tartar concentration of being added.
Table 1 calcining speed; Additive influence KMp3 3% H
2O 200MPa 270 150 minutes
| Additive (weight %) | The % semihydrate | |
| Sodium succinate | K 2SO 4 | |
| 0.0 | 0.0 | 92.15 |
| 0.1 | 0.0 | 93.75 |
| 1.0 | 0.0 | 89.37 |
| 0.0 | 0.1 | 92.81 |
| 0.0 | 1.0 | 91.17 |
| 0.1 | 1.0 | 88.65 |
The pressure that data declaration shown in the following table 2 changes and the influence of water content, for the briquet of laboratory, although proof has positive benefit in 30 minutes calcination time scope, but in the time of 2.5 hours, be not to influence overall degree of calcination energetically, because till this moment, finished transformation to semihydrate.
Table 2 calcining speed; Water to various gypsum and pressure influence under 270 , 150 minutes
| The gypsum source | Pressure (Mpa) | % added from | The % semihydrate |
| KMp3 | 100 | 1 | 92.49 |
| KMp3 | 100 | 3 | 93.25 |
| KMp3 | 100 | 5 | 92.66 |
| LDSG | 14 | 1 | 94.65 |
| LDSG | 14 | 5 | 94.93 |
| LDSG | 14 | 10 | 95.14 |
| LDSG | 50 | 1 | 94.38 |
| LDSG | 50 | 5 | 94.92 |
| LDSG | 50 | 10 | 95.09 |
| LDSG | 200 | 1 | 95.07 |
| LDSG | 200 | 3 | 94.11 |
| LDSG | 200 | 5 | 94.74 |
| LDSG | 200 | 10 | 95.14 |
Consider the easy degree of briquetting, the exemplary gypsum briquet that the method that can pass through to be disclosed transforms is a big briquet (for example the water of 4-5% and on machine without the peak pressure that firmly reaches) under maximal humidity and peak pressure.Humidity 5% and the briquet under the high pressure go on well, but have some risks, and promptly for the gypsum of some type, its dihydrate can cling briquetting press and therefore reduce possibility essential pressure and/or water content.If when making briquet, dihydrate is too dried, then briquetting press becomes very noisy and need to add extra water on machine.In addition, after forming briquet, can be with the water spray thereon increasing calcining speed, but better be before briquet forms, water to be added on the material and on compressibility, help out.
From what has been discussed above as seen, different factors can influence incinerating speed and the easy degree of making the better quality briquet that is suitable for this method.Find that also these parameters also can influence the water requirement of the semihydrate plaster that is produced.The water requirement characteristic can influence finished product.For example, if initial mortar is to make with less water, then the intensity of set gypsum mortar is with high many.In this case, the density of the gypsum matrix of being made by the alpha-hemihydrate that is disclosed of finally solidifying is higher than traditional alpha-hemihydrate.Therefore, improved the strength characteristics of final gypsum matrix product.
In the manufacturing of alpha-hemihydrate plaster, the dehydration of gypsum takes place by this way, i.e. the crystallization of alpha-hemihydrate is grown with bulk form.Once grinding, promptly produce the alpha-hemihydrate fine powder of low water demand.Along with changing semihydrate quickly into, change the also more generation of piece of α-type into.Be not bound by any theory, seem the method that disclosed to have created the condition that can change the semihydrate material forms rapider and more completely into for the briquet in calcining compartment, this semihydrate material causes low water requirement after grinding subsequently.Be present in that high temperature, high density of material and high-moisture in the briquet in the calcining compartment causes the dehydration of gypsum and to the transformation of stable semihydrate bulk form.Once these calcining briquets of subsequent grinding, promptly produce the particulate alpha-hemihydrate plaster of low water demand.
Determine that a parameter in the water requirement is to grind.Can utilize many grinding options to come optimization water requirement feature, but be the low-cost manufacturing works of simulation environment, can select simple as far as possible polish process.Use following program to grind briquet.Use the customization hammer mill milling apparatus and the ventilation system that comes from the Shop-Vac Canada Ltd. in Burlinton city, Ontario, Canada (wet/dry vacuum gas blower of one 3.0 horsepowers of the Analytical Instruments Ltd. that comes from Minneapolis city, Minn. as shown in Figure 11, one 4.5 horsepowers noiseless is powerful to wet/dry vacuum air pump and the efficient disposable filtering bag (906-71) that is used for sample collection) and, grind briquet (Figure 11) by one 100 order mesh screen.Then, having 60 * 1 at one 7.5 inch diameter * 8 inch height " in the cylindrical ball milling container of steel ball, the QT12/QT66 rotary roller that uses the Lortone Inc.of Mukilteo that comes from Washington, DC was with Powder samples ball milling 15 minutes.
Be ground to about 3500cm
2The intensity of the final product that the surface-area maximizing of/g is made by alpha-hemihydrate also reduces the water requirement of alpha-hemihydrate.Term used herein " surface-area " refers to Bu Laiyin (Blaine) surface-area of various materials.Use standard A STM testing method C204-00 to test this surface-area.In an example, alpha-hemihydrate has about 2500 to 4500cm
2The Bu Laiyin surface-area of/g.Definite, when alpha-hemihydrate has about 2500 to 4000cm
2During the Bu Laiyin surface-area of/g, can obtain useful characteristic.For example, under the situation of constant interpolation water, measure in (for example 44ml water/100g plaster (may and keeping off border water requirement in fact)), the measurement of pouring into a mould the cake diameter is caused being inversely prroportional relationship with actual water requirement.Ball milling is calcined, pulverizes and followed to the laboratory briquet to increase fineness, and it causes higher cake diameter, and therefore reduces water requirement.Once being ground to about 3500cm
2/ g, the cake diameter promptly reduces, and causes water requirement to increase (referring to following table 3).
Table 3. cast continuity cake diameter; The influence of time in ball mill
| In ball mill the time | The Bu Laiyin surface-area | Cast continuity cake diameter (mm) |
| 0 | 3113 | 108.5 |
| 15 | 3580 | 120 |
| 30 | 4438 | 119 |
| 60 | 5957 | 115 |
| 120 | 83.5 |
That studies two types of gypsum (Kerr McGee and LDSG material) is used to make the influence of the pressure of briquet for water requirement.For LDSG, along with the increase of pressure in the briquet manufacturing, the change of water requirement is very little, but longer calcination time has reduced water requirement really.If use Kerr McGee gypsum to replace LDSG, as shown in Figure 12, water requirement reduces to 37.5ml/100g plaster by about 43ml/100g plaster.As shown in Figure 13, the result of test also shows the pressure increase that is used to make briquet, can reduce gained through grinding the water requirement of semihydrate.Yet under long calcination time (for example KMp is 3150 minutes), water requirement has reduced and along with the increase of briquet pressure, has not almost had other benefit (Figure 13).In granularity and in shape, Kerr McGee gypsum is wideer and make briquet more closely under higher pressure than LDSG.
Inspection is useful through the photo of calcining briquet for definite possible reason.As the photo of making under 14Mpa through the calcining briquet that provides among Figure 14 A, it is presented between the semihydrate crystallization of having grown in the calcining briquet sizable space.Under 200Mpa, the semihydrate crystallization of few many in space and growth more may be interfering with each other when growth, especially crystalline growth the fastest vertically on.This interferential result stops the crystallization of growth than the unrestricted crystallization of carrying out down shorter and thicker (Figure 14 B).Figure 14 C shows under the same conditions, if make KMG be loose be scattered in the water powder and in autoclave the crystal form of growth gained.For relatively, Figure 14 D also shown under same condition, has been dried powder and identical KMG gypsum after calcining.It is minute hand that dried calcining has kept the little needle-like and the loose suspension growth of laminar initial gypsum crystallization and semihydrate, both make on the low water demand plaster all undesirable.
The high pressure of briquet and limited spatial interference crystalline growth so that be rendered as the form shown in Figure 14 E by the semihydrate crystallization of KMG growth.Be subjected to the influence in the density and the orientation of gypsum crystallization with the crystallization of growth of the form of tight compression and the alpha-hemihydrate parallel with the briquet surface, the α semihydrate is derived from this gypsum crystallization.For showing the macroscopic crystalline growth on relevant briquet surface, the reference range of 1mm taken and indicated under than the littler enlargement ratio of other photo by the photo of Figure 14 E.
Also comprised the initial KMG photo (Figure 14 F) that is used for reference, it is littler several times than the α semihydrate crystallization of final gained in order to proof KMG crystallization before calcining.Calcine rock under the same conditions and produce different materials, pure as shown polycrystalline Du Lubai (Drumbo) rock specimens (Figure 14 G) and single crystal transparent gypsum sample (Figure 14 H).Produce the littler crystallization together of some good binding through incinerating Du Lubai rock, and selenitum produces fairly regular minute hand structure, it is as loose the forcing together of a pile pencil, multilated easily when touching.The photo (Figure 141) that has also comprised the micro-meter scale that is used for reference, the distance between two minimum scales is 10 microns.The photo of all Figure 14 is all taken under this enlargement ratio, except Figure 14 E that has illustrated.
Be suitable for making in the water content ranges of the briquet that discloses, along with the water content in the briquet increases, water requirement obtains improvement.Figure 15 shows that because KMG has been arranged, along with the increase of water content in the briquet, the semihydrate water requirement reduces.Similarly, the calcining of longer time further reduces water requirement under these pressurization water vapor conditions, highlights the advantage with a faster calcining method.Do not wish to be bound by theory, higher water content can be assisted the thermal conduction in the briquet, thereby assists calcining.In addition, water can be assisted the crystallisation process of semihydrate, thereby accelerates calcining speed and reduce water requirement.Can realize lower water requirement by the bigger block crystallization of growth, this bigger block crystallization can produce wide size-grade distribution through grinding, and when mixing with water, it is then compressed together more thick and fast.
Find that also additive can improve the water requirement of the plaster that novel method produced thus.As shown in Figure 16, under similar calcination condition, add a small amount of sodium succinate and cause the water requirement lower than undressed gypsum.In wet autoclave method, in making the α semihydrate, will be used for regulating crystal habit such as the additive of succsinic acid or vitriolate of tartar.Yet, as shown in Figure 16, in the embodiment of institute's revealing method,, make selected additive and usage quantity optimization to obtain useful result at process condition.
Under high pressure that is disclosed and water content, form disclosed generally have the volume of voids of about 30-50 volume % through calcining alpha-hemihydrate briquet.In one embodiment, the volume of voids of dihydrate briquet is about 40 to 50 volume %.Figure 17 describe various exemplary through calcining briquet, selenitum monocrystalline (" selenitum crystallization ") and the bar graph of the volume of voids (% represents with volume) of gypsum rock, the data of its demonstration volume of water and volume of air.
Should point out the simple result of void fraction percent before the overall void fraction percent of calcining briquet may not be calcining.As shown in Figure 18, the voids content that relatively shows the briquet that contains 1% water of the volume of voids of LDSG briquet before calcining is lower than the briquet that contains 3% water, yet after the calcining, the briquet that contains 3% water shows lower void fraction percent.The calcining of low hole appears under the condition that produces minimum water requirement.
After the calcining, before the briquet of handling through autoclave is used to make final Powdered alpha-hemihydrate product, be dried and grind to form fine powder usually.As if consider the dry feature of briquet, do not wish to be subjected to any one theory, the water in the briquet briquet hole that kept in calcining, losing.
Figure 19,20 is that the diagram of the dry data of briquet shows.Use the drying in precision optical machinery convection oven-model STM 135 (Illinois, USA Chicago) chamber that experimentizes.Make the experimentize pulverizing of briquet in the chamber of mincer by hand, obtain the particle of 0-6mm size.Use experimentize smooth grinding in the chamber of mortar and pestle.As seen in Figure 19, if dry in dish, be used for to respectively 211 and 158MPa under the lab investigation of the big KM16 briquet that contains 2% water made, be about 4 days (about 5700 minutes) in 104 time of drying.Under 194 , drying was finished in (about 1500 minutes) at about 24 hours.For the drying operation that enlarges, time of drying even longer in being open to airborne autoclave.If briquet is positioned in the basket that opens wide in the autoclave, blow over briquet with warm air, then can further reduce time of drying.In a case method, also vacuum can be used for drying, to increase drying rate.
Figure 20 is in another experiment, big comparison of not grinding the drying rate of briquet and big grinding briquet.Make the briquet of mincer pulverizing through grinding by hand, and heat with fan heater simultaneously.Total pulverizing time is about 5 minutes and in crushing process, 8% the water loss of having an appointment.Be astoundingly, in the time of in putting back to baking oven, slower than the overall drying rate of complete briquet through the overall drying rate of pulverized powder.Some sample losses are arranged in pulverizing, thereby reduce the size of pulverizing bed, it should help powder dry faster in theory.Do not wish to be subjected to any special one theory, this experiment prompting is if there is good air cycle to come drying material, and the speed when then Ci Shi speed ratio briquet surface-area is subjected to exposing is faster, and this perhaps is an independent factor.Be about 5 to 6 hours and for pulverizing bed, be about 22 hours time of drying overall time of drying.Laboratory test data is proved in semi-plant.
As the alpha-hemihydrate of routine, announcement can be used for the composition and the product of multiple material through the alpha-hemihydrate of improvement.The water requirement of the alpha-hemihydrate that discloses be per 100 the gram (g) less than about 50 milliliters (ml), this water requirement is considered to the typical water requirement of dry block autoclave calcinate.For forming one type plaster product, another exemplary alpha-hemihydrate has the water requirement of the about 42ml water of every 100g alpha-hemihydrate.This water requirement is enough to be used in multiple answering week.For the announcement alpha-hemihydrate, under additive-free situation of adding mixture to, possible water requirement overall range may be 35 to 50ml/g, when crystal habit conditioning agent additive is perhaps arranged in alpha-hemihydrate/water mixture, perhaps is 28 to 40ml/g.For example, use additive, water requirement can be about 32 to 40ml/g.In another example, water requirement is about 37 to 42ml/g.
The alpha-hemihydrate that is disclosed can be used for the hypogee, it comprises the excavation in tunnel and corridor, and is used to support sub-terrain operations.Other example comprises automatic leveling ground plaster, is used for installing rapidly the rapid repairing slurry of concrete and/or asphalt roofing and/or road, fiber and/or fragment gusset plate product, porous foam shape plaster wall inner panel, the porous foam shape sorbent material that uses as oily tackiness agent, solvent cement, animal habitat are with coarse sand grain and be used to make material for ceramic usefulness mould.By cost and the strength characteristics prompting of announcement through the product made of alpha-hemihydrate of improvement, it is applicable to ground, and the advantage that surmounts current competitive product and method is provided really.Test shows, under flowability that equates and water content, for with the identical tackiness agent/husky ratio of competitive products LevelrockTM 2500 (make and can buy) from it by the USG in Illinois, USA Chicago, the alpha-hemihydrate that is disclosed is improved to some extent.Referring to following table 4.
Table 4. and Levelrock
TMThe 2500 exemplary alpha-hemihydrates of comparing that disclose intensity data
| The semihydrate material | The weight of semihydrate (g) | Husky weight (g) | The weight of water (g) | The weight (g) of cube test specimen | Compressible intensity (psi) |
| Levelrock TM 2500 | 343 | 1157 | 357.6 | 224.0 | 819 |
| Levelrock TM 2500 | 399 | 1098 | 321.6 | 234.2 | 1534 |
| Exemplary α-the semihydrate that discloses | 343 | 1157 | 357.6 | 236.2 | 1131 |
| Exemplary α-the semihydrate that discloses | 343 | 1157 | 357.6 | 226.0 | 1007 |
| Exemplary α-the semihydrate that discloses | 399 | 1098 | 321.6 | 219.1 | 1729 |
Data from table 4 as seen, under equal cube test specimen weight, the alpha-hemihydrate that discloses produce ground leveling product with higher compressive strength, it is higher than the commercially available prod of probably being made by conventional alpha-hemihydrate.In addition, because the manufacturing of the alpha-hemihydrate that discloses is obviously faster and more cheap, so announcement can be used for other application with high costs up to now through the alpha-hemihydrate of improvement.
Can incorporate additive into to be used for that the material of construction made from the α semihydrate is installed immediately and rapidly.Sand is a kind of additive that can be used for alpha-hemihydrate, and it is in the composition of incorporating into traditionally as materials such as automatic leveling ground plaster.The alternate embodiment based on the composition of matter of gypsum that is disclosed replaces at least some sand with flying dust, in order to the water requirement that reduces the improvement alpha-hemihydrate with increase the intensity that improves the product that alpha-hemihydrate makes thus.Can obviously reduce the water requirement of cast tackiness agent aggregate mix by replace (about 0-30%) sand to gather materials with flying dust.
As shown in Figure 21, replace at least some sand, but keep the constant of water content with flying dust, can increase a little solidify the compressive strength of alpha-hemihydrate of the drying that discloses and grinding.On the identical sample that contains flying dust, when reducing water content subsequently, can be observed compressive strength more obviously increases, and the water requirement of new minimizing has been described.Even if add very small amount of flying dust, the increase of article intensity also can take place.
The granularity data of Figure 22 A and 22B shows the granularity of two kinds of dissimilar plaster stone and the distributed data of shape.For the initial starting material identical with 22B with Figure 22 A, Figure 23 A-23C is presented at plaster stone and has stood after the exemplary method disclosed herein, the data identical with 22B with Figure 22 A.Particle size distribution data shows that the material of the drying/grinding that discloses more is bimodal shape than conventional dry bulk through calcining/grinding product on size distribution.Do not wish to be subjected to any one theory, should believe flying dust interpolation in addition can be outside the size-grade distribution of whole matrix (for example tackiness agent, flying dust and sand), thereby further improve the water requirement of Powdered alpha-hemihydrate.
What should emphasize is, through the foregoing description of improvement α calcium sulfate hemihydrate, make the method for α calcium sulfate hemihydrate and only be possible example execution with this product of making through improvement α calcium sulfate hemihydrate.For the foregoing description, can carry out multiple change and modification.Wish that in this article all such modifications and change all are included within the category of this disclosure and following claim.
Claims (38)
1. method for preparing α type calcium sulfate hemihydrate, it comprises: make calcium sulfate dihydrate (CaSO under the pressure greater than 14 megapascal (MPa)s (MPa)
42H
2O)
Form a briquet;
Calcine described briquet;
Described calcium sulfate dihydrate briquet is converted into calcium sulfate hemihydrate (CaSO
4 H
2O) [α-type] (" alpha-hemihydrate ") briquet; And
Dry described alpha-hemihydrate briquet.
2. method according to claim 1, it further comprises the described exsiccant alpha-hemihydrate briquet of grinding.
3. method according to claim 2, wherein said alpha-hemihydrate through grinding has bomodal size distribution.
4. method according to claim 1, it further comprises:
The described exsiccant alpha-hemihydrate of rough grinding briquet; And
The described exsiccant alpha-hemihydrate of smooth grinding subsequently.
5. method according to claim 1, it further comprises:
With described exsiccant alpha-hemihydrate briquet grind into powder; And
Described Powdered alpha-hemihydrate is mixed with water.
6. method according to claim 1, it further comprises:
With described exsiccant alpha-hemihydrate briquet grind into powder; And
Described Powdered alpha-hemihydrate is mixed with water and flying dust (fly ash).
7. method according to claim 1, the volume of wherein said calcium sulfate dihydrate briquet are about 0.125 to 125 cubic inch.
8. method according to claim 1, the volume of wherein said calcium sulfate dihydrate briquet are about 1 to 27 cubic inch.
9. method according to claim 1, the volume of wherein said calcium sulfate dihydrate briquet are about 1 to 8 cubic inch.
10. according to the arbitrary described method of claim 7 to 9, wherein calcination time in about 30 minutes to 6 hours scope to finish in fact by of the conversion of described calcium sulfate dihydrate to described alpha-hemihydrate.
11. method according to claim 7, wherein said calcination time is in about 30 minutes to 2.5 hours scope.
12. method according to claim 7, wherein said calcination time is in about 1 hour to 2 hours scope.
13. method according to claim 1, wherein in order to the described pressure that forms described calcium sulfate dihydrate briquet greater than 14 scopes to about 500 megapascal (MPa)s (Mpa).
14. method according to claim 13, wherein said calcination time in about 30 minutes to 6 hours scope to finish in fact by of the conversion of described calcium sulfate dihydrate to described alpha-hemihydrate.
15. method according to claim 1, wherein said in order to the pressure that forms described calcium sulfate dihydrate briquet in about 50 to 320Mpa scope.
16. method according to claim 15, wherein said in order to the pressure that forms described calcium sulfate dihydrate briquet in about 100 to 200Mpa scope.
17. method according to claim 15, the volume of voids of wherein said alpha-hemihydrate briquet are about 30 to 49% of described briquet cumulative volume.
18. method according to claim 15, wherein water constitutes about 0 weight % of described calcium sulfate dihydrate briquet to 12 weight %.
19. method according to claim 15, it further comprises:
The described exsiccant alpha-hemihydrate of rough grinding briquet; And
The described exsiccant alpha-hemihydrate of smooth grinding subsequently;
Wherein said alpha-hemihydrate through grinding has bomodal size distribution.
20. method according to claim 1, the volume of voids of wherein said alpha-hemihydrate briquet are about 30 to 49% of described briquet cumulative volumes.
21. method according to claim 1, the volume of voids of wherein said alpha-hemihydrate briquet are about 40 to 49% of described briquet cumulative volumes.
22. method according to claim 1, wherein water constitutes about 0 weight % of described calcium sulfate dihydrate briquet to 12 weight %.
23. method according to claim 1, wherein water constitutes about 1 weight % of described calcium sulfate dihydrate briquet to 5 weight %.
24. method according to claim 1, wherein water constitutes about 2 weight % of described calcium sulfate dihydrate briquet to 3 weight %.
25. a product of being made by mixture, described mixture comprises:
Method according to claim 2 make through grinding alpha-hemihydrate; And water.
26. according to claim 25 described products, it further comprises sand.
27. according to claim 25 described products, it further comprises flying dust.
28. calcium sulfate hemihydrate (CaSO
4 H
2O) [α-type] (" alpha-hemihydrate "), its
Comprise:
The crystallization of alpha-hemihydrate, it grows to form haptophore together;
Wherein with under the pressure that is less than or equal to 14 megapascal (MPa)s (Mpa) compare by the alpha-hemihydrate crystalline volume of voids that forms of dihydrate briquet of compression, described haptophore have minimizing in fact bunch between volume of voids.
29. alpha-hemihydrate according to claim 28 wherein can grind described haptophore to produce the block crystallization of alpha-hemihydrate.
30. alpha-hemihydrate according to claim 29, wherein said alpha-hemihydrate through grinding has bomodal size distribution.
31. alpha-hemihydrate according to claim 28, the wherein said volume of voids that reduces in fact is included as about 30 to 50% the volume of voids of described crystalline volume.
32. alpha-hemihydrate according to claim 28, the wherein said volume of voids that reduces in fact is included as about 40 to 50% the volume of voids of described crystalline volume.
33. a drying, calcium sulfate hemihydrate (CaSO through grinding
4 H
2O) [α-type] (" alpha-hemihydrate "), it is changing through incinerating calcium sulfate dihydrate briquet by compression under greater than the pressure of 14 megapascal (MPa)s (Mpa); Wherein said drying, the alpha-hemihydrate through grinding have that per 100 grams (g) are dry, the alpha-hemihydrate through grinding is less than the water requirement of 50 milliliters (ml).
34. alpha-hemihydrate according to claim 33, wherein said alpha-hemihydrate is formed by gypsum, and described gypsum is obtained by at least a following method as by product: the production of flue gas desulfurization (FGD), titanium dioxide or the production of phosphate fertilizer.
35. alpha-hemihydrate according to claim 33, the described pressure that wherein is used to form described calcium sulfate dihydrate briquet is in about 100 to 200Mpa scope.
36. alpha-hemihydrate according to claim 35, wherein water constitutes about 0 weight % of described calcium sulfate dihydrate briquet to 12 weight %.
37. alpha-hemihydrate according to claim 36, the volume of wherein said calcium sulfate dihydrate briquet are about 1 to 27 cubic inch.
38. a method for preparing alpha-calcium sulphate semihydrate powder, it comprises:
Under pressure, make calcium sulfate dihydrate (CaSO greater than 14 megapascal (MPa)s (MPa)
42H
2O) form briquet, the volume of wherein said calcium sulfate dihydrate briquet be about 0.125 to 125 cubic inch and wherein water constitute about 0% to 12 weight % of described calcium sulfate dihydrate briquet;
Calcine described briquet, wherein said calcination time in about 30 minutes to 6 hours scope to finish described calcium sulfate dihydrate in fact to the conversion of described alpha-hemihydrate;
Make described calcium sulfate dihydrate briquet be converted into calcium sulfate hemihydrate (CaSO
4 H
2O) [α-type] (" alpha-hemihydrate ") briquet;
Dry described alpha-hemihydrate briquet, the volume of voids of wherein said alpha-hemihydrate briquet accounts for about 30 to 49% described briquet cumulative volume;
The alpha-hemihydrate briquet of described drying is ground to form the alpha-hemihydrate powder, wherein said Powdered alpha-hemihydrate has bomodal size distribution, and wherein said Powdered alpha-hemihydrate has the water requirement of per 100 gram (g) Powdered alpha-hemihydrates less than 50 milliliters (ml).
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|---|---|---|---|
| US45620703P | 2003-03-20 | 2003-03-20 | |
| US60/456,207 | 2003-03-20 | ||
| US10/800,780 | 2004-03-15 |
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| TWI710358B (en) * | 2018-02-16 | 2020-11-21 | 日商Gc股份有限公司 | Dental plaster powder |
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| ES2873113T3 (en) * | 2006-06-29 | 2021-11-03 | Yoshino Gypsum Co | Methods for making calcined plaster and plasterboard |
| WO2012054009A1 (en) * | 2010-10-19 | 2012-04-26 | Jiin-Huey Chern Lin | Method for preparing a hardened calcium sulfate dihydrate block and use thereof |
| US10280288B2 (en) | 2013-12-06 | 2019-05-07 | Georgia-Pacific Gypsum Llc | Calcium sulfate crystals and methods for making the same |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5015449A (en) * | 1987-05-22 | 1991-05-14 | Promineral Gesellschaft Zur Verwendung Von Mineralstoffen Mbh | Process for making construction grade calcium sulfate alpha-hemihydrate from moist finely divided gypsum obtained from a power plant flue gas desulfurization |
| US5562892A (en) * | 1995-01-26 | 1996-10-08 | Kirk; Donald W. | Process for the production of alpha hemihydrate calcium sulfate from flue gas sludge |
-
2004
- 2004-03-18 CN CNB2004800121481A patent/CN100352767C/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5015449A (en) * | 1987-05-22 | 1991-05-14 | Promineral Gesellschaft Zur Verwendung Von Mineralstoffen Mbh | Process for making construction grade calcium sulfate alpha-hemihydrate from moist finely divided gypsum obtained from a power plant flue gas desulfurization |
| US5562892A (en) * | 1995-01-26 | 1996-10-08 | Kirk; Donald W. | Process for the production of alpha hemihydrate calcium sulfate from flue gas sludge |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI710358B (en) * | 2018-02-16 | 2020-11-21 | 日商Gc股份有限公司 | Dental plaster powder |
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