177 results about "Hemihydrate" patented technology

The invention belongs to the field of building decoration materials, and discloses a GRG gypsum composite reinforced material and a preparation method thereof. The high-strength concrete is prepared from the following components in parts by weight: 45 to 65 parts of alpha-semi-hydrated gypsum, 12 to 20 parts of composite reinforced fiber, 0.5 to 2 parts of graphene nanofiber, 2 to 5 parts of nano silica fume, 5 to 10 parts of ethylene-vinyl acetate copolymer latex powder, 1 to 2.5 parts of hydroxypropyl methyl cellulose, 0.1 to 0.8 part of polycarboxylic acid type water reducing agent, 1 to 4 parts of calcium stearate, 3 to 8 parts of vermiculite powder and 28 to 40 parts of deionized water. Aiming at the problems that an existing GRG material is insufficient in mechanical property, low in fireproof grade, poor in thermal performance, poor in durability and the like, a multi-dimensional synergistic enhancement system is constructed by adopting composite reinforced fibers, functional nanofiller and a gradient preparation process, the problems of dispersion and interfacial compatibility of the nanofiller are solved, and the comprehensive performance of the GRG material is improved. The performance breakthrough of high strength, high fire resistance, low heat conduction and long durability is realized.

The invention discloses a method for selectively and efficiently removing impurities in desulfurized gypsum and preparing high-quality alpha-semi-hydrated gypsum, which comprises the following steps: (1) removing organic impurities in the desulfurized gypsum by utilizing flotation, then removing soluble impurities by washing, and aerating air to oxidize calcium sulfite into calcium sulfate dihydrate while washing, then carrying out acid leaching in a hydrochloric acid solution to remove insoluble impurities, taking out and drying to obtain treated desulfurized gypsum; and (2) adding the desulfurized gypsum treated in the step (1) into a carboxylic acid aqueous solution to carry out solution crystallization reaction, adding potassium carboxylate into the carboxylic acid aqueous solution to regulate and control the crystallization rate and crystal morphology, carrying out solid-liquid separation after the reaction is finished, and washing, drying and ball-milling the solid to obtain the high-quality alpha-semi-hydrated gypsum powder. The alpha-semi-hydrated gypsum product obtained by the invention is high in purity, and the hydrated body has high absolute dry compressive and flexural strength.

The invention relates to the field of preparation of concrete materials, and particularly discloses a high-matching-degree concrete shrinkage compensation additive and application thereof. The additive comprises the following components in parts by weight: 3-20 parts of aluminoferrite mineral powder and 6-26 parts of a modified regulating agent. Wherein the preparation of the modified regulating agent comprises the following steps: (1) mixing a composite modifier composed of dihydrate gypsum powder, a regulating agent and sulfate, calcining in stages, and quenching after the calcination is completed, so as to obtain the beta-type modified semi-hydrated gypsum. And (2) uniformly mixing the beta-type modified semi-hydrated gypsum with anhydrous gypsum powder, then uniformly mixing the obtained mixed powder with liquid polyethylene glycol, standing and aging to obtain the modified regulating agent. According to the high-matching-degree concrete shrinkage compensation additive, expansion can be precisely regulated and controlled in stages, and the adopted industrial solid waste serves as the raw material, so that the cost is reduced, and resource utilization is achieved.

The invention relates to the technical field of building materials, and discloses a gypsum-containing lightweight waterproof wear-resistant mortar and a preparation method thereof, the gypsum-containing lightweight waterproof wear-resistant mortar comprises the following components by weight: 90-110 parts of modified beta-semi-hydrated gypsum; 20 to 40 parts of Portland cement; 10 to 25 parts of calcium aluminate cement; 5 to 15 parts of active silicate-carboaluminate; 2 to 8 parts of nano SiO2; 2 to 5 parts of nano A < l > 2O3; 15 to 30 parts of glass beads; 10 to 25 parts of modified foamed ceramic microbeads; 0.8 to 3 parts of chopped basalt fiber; and 0.5 to 2 parts of PVA fiber. According to the invention, by combining the nano-SiO2 reinforcing agent, the nano-Al 2O3 reinforcing agent, a negative pressure exhaust process and a fiber reinforcing technology, the mechanical property, durability, permeability resistance and thermal insulation property of the mortar are improved, and higher strength, longer service life and more excellent environmental adaptability are realized.

To provide a cement composition comprising Portland cement and hemihydrate gypsum, which can form a mortar hardened body having excellent dimensional stability in water.SOLUTION: There is provided a cement composition comprising a hydraulic component composed of Portland cement and hemihydrate gypsum and a fine aggregate. The total amount of soluble silica and soluble alumina, measured in accordance with JIS A 1145:2017 [Method of test for alkali-silica reactivity of aggregates by chemical method], is less than 50 mmol / L per 25 g of a fine aggregate. The content of the fine aggregate is 30 to 80 mass% based on the total amount of the cement composition. The content of the Portland cement is 20 to 60 mass% and the content of the hemihydrate gypsum is 40 to 80 mass%, based on the total amount of the hydraulic component.SELECTED DRAWING: None

The invention discloses a beneficiation method of high-quality phosphoric ore pulp for producing hemihydrate-dihydrate phosphoric acid, and relates to the technical field of phosphorite beneficiation. The method comprises the following steps: primarily crushing medium-low-grade collophanite, grinding and grading to obtain flotation pulp; after sulfuric acid and a reverse flotation collecting agent are added into flotation pulp for pulp mixing and mineralization, the flotation pulp is pumped into a roughing flotation column for roughing, and roughing concentrate is obtained; the roughing concentrate is subjected to size mixing and pumped into a cyclone set to be subjected to cyclone classification, and sand setting ore pulp with sesquioxide reduced is obtained; carrying out size mixing on the sand setting ore pulp, and pumping the ore pulp into a fine flotation column to obtain fine phosphoric ore pulp; concentrating the concentrated ore pulp through a thickener, pressurizing and filtering, and supplying the concentrated ore pulp to a semi-hydrated-dihydrated phosphoric acid device for use. A flotation column is adopted for roughing, part of sesquioxide in the phosphoric ore pulp is removed through low-pressure rotational flow grading, deep magnesium removal is conducted through a fine selection technology, magnesium oxide in the ore pulp is further reduced, and the phosphoric ore pulp meeting the production requirement of the semi-hydrate-dihydrate phosphoric acid technology is obtained through concentration and filter pressing dehydration of a thickener.

A process for the production of alpha-calcium sulphate hemihydrate, the process comprising the steps of: providing an input comprising particulate gypsum and an impurity; providing water; mixing the input and the water to form a gypsum slurry; maintaining the gypsum slurry under raised pressure and temperature to convert the particulate gypsum into alpha-calcium sulphate hemihydrate; and providing an alpha-calcium sulphate hemihydrate slurry; in order to provide an output comprising alpha-calcium sulphate hemihydrate with a reduction in the amount or activity of an impurity compared to the input or wherein the output comprises the impurity in a changed form compared to the input.

The invention discloses a preparation method of low-alkali plant-growing concrete with full-dosage phosphogypsum and recycled aggregate, and belongs to the technical field of resource utilization of industrial solid waste and building solid waste and ecological building materials. The low-alkali plant-growing concrete containing the full-dosage phosphogypsum and the recycled aggregate is prepared from the following raw materials in parts by weight: 180 to 190 parts of semi-hydrated phosphogypsum, 1365 to 1375 parts of the recycled aggregate, 55 to 65 parts of cement, 17 to 22 parts of fly ash, 0.4 to 0.6 part of a water-retaining agent, 32 parts of electrolytic manganese residues and 0.8 to 1.2 parts of a water reducing agent. The low-alkali plant-growing concrete prepared by the invention realizes full utilization of solid wastes, construction of a low-alkali environment and cooperation of a suitable pore structure and plant nutrition supply, and the comprehensive performance meets ecological engineering requirements.

The application discloses a kind of composite gel-physical foaming synergistic carbon dioxide foam concrete preparation process, carbon dioxide foam concrete, by mass parts, consisting of following components: sulphate cement 15-45 parts, hemihydrate gypsum 10-50 parts, Portland cement 5-15 parts, mineral powder 0-30 parts, gypsum retarder 0-0.3 parts, retarder 0.2-0.4 parts, water reducing agent 0.2-0.4 parts, calcium stearate 0.2-0.6 parts, hydroxypropyl methylcellulose ether (HPMC) 0.1-0.3 parts, water-cement ratio 0.2-0.45, prefabricated foam 5-15 parts.Sulphate cement, Portland cement and hemihydrate gypsum are mixed to prepare carbon dioxide foam concrete when specific mass ratio, can play the hydration synergistic effect between three, and then can greatly improve the mechanical properties of carbon dioxide foam concrete.

The invention discloses a morphology control method for preparing alpha-semi-hydrated gypsum by using desulfurized gypsum in an ethylene glycol-water system, which comprises the following steps: (1) mother liquor preparation: mixing inorganic salt, a crystal modifier and an ethylene glycol water solution to prepare a mother liquor; (2) feeding and crystal transformation: feeding the desulfurized gypsum into the mother liquor, mixing to form turbid liquid with specific solid content, and carrying out crystal transformation reaction under the normal-pressure hydrothermal condition of 80-100 DEG C; and (3) product collection: carrying out solid-liquid separation on the turbid liquid after the crystal transformation reaction, and washing and drying the solid phase to obtain the alpha-semi-hydrated gypsum. The invention provides a morphology regulation method of alpha-semi-hydrated gypsum prepared from desulfurized gypsum in an ethylene glycol water system, which can be used for preparing alpha-semi-hydrated gypsum with four different morphologies of nickel coin shape, short column shape, long rod shape and whisker shape at a relatively high conversion rate, and realizing large-range flexible regulation of average length-diameter ratio from 0.1-80.

The invention relates to the technical field of civil engineering materials, in particular to a cement-based composite coiled material for emergency rescue and a rapid construction method.The cement-based composite coiled material for emergency rescue comprises a stereoscopic three-dimensional structure fabric and hydraulic cement-based filler, the stereoscopic three-dimensional structure fabric is filled with the hydraulic cement-based filler, and the hydraulic cement-based filler is arranged in the stereoscopic three-dimensional structure fabric. One side of the bottom of the three-dimensional structure fabric further comprises a waterproof wear-resistant coating; the hydraulic cement-based filler is prepared from the following components in parts by weight: 30 to 45 parts of high belite sulphoaluminate cement, 10 to 20 parts of ordinary Portland cement, 10 to 15 parts of fly ash, 5 to 8 parts of alpha-semi-hydrated gypsum, 3 to 5 parts of an expanding agent, 0.5 to 1.5 parts of a polycarboxylic acid type water reducing agent, 25 to 35 parts of silica sand and 0.1 to 0.8 part of a thickening time control agent. The prepared cement-based composite coiled material for emergency rescue has good tensile property, and the prepared cement-based composite coiled material meets the one-day compressive strength gt; the 28-day compressive strength is gt; the pressure is 65 MPa; the one-day tensile strength is gt; 3.5 MPa, 28-day tensile strength gt; and the performance index requirement of 5.5 MPa is met.

The present invention relates to the technical field of waste recovery, and provides a method for preparing a hemihydrate gypsum powder from phosphogypsum by means of an atmospheric salt solution process, and a hemihydrate gypsum powder. The method comprises: preparing a slurry from a mixed liquid of a salt and a crystal modifier and purified phosphogypsum, wherein the crystal modifier is a betaine compound with pH responsiveness; and adjusting the pH value of the slurry on the basis of the isoelectric point of the crystal modifier and the required length-diameter ratio of hemihydrate gypsum crystals, subjecting the slurry to a constant-temperature dynamic reaction, and filtering same, thereby obtaining a hemihydrate gypsum powder, wherein when the pH value of the slurry is greater than the isoelectric point of the crystal modifier, the length-diameter ratio of the hemihydrate gypsum crystals increases, and when the pH value of the slurry is less than the isoelectric point of the crystal modifier, the length-diameter ratio of the hemihydrate gypsum crystals decreases. By using the betaine compound as the crystal modifier, hemihydrate gypsum crystals with different length-diameter ratios can be obtained by adjusting the pH value of the slurry, and therefore the regulation and control of the crystal morphology of hemihydrate gypsum are achieved and exhibit a certain pattern.

A crystalline aceclodine HCl hemihydrate of formula (I): having a DSC onset peak at a value between 137.08 DEG C and 139.08 DEG C and / or an X-ray powder diffraction pattern with a characteristic peak at 17.7 + / -0.2 and / or 20.47 + / -0.2, represented by a 2-theta value (2 theta).

The present invention belongs to the field of pharmaceutical synthesis technology, and in particular to a new crystal form of fosfomycin sodium and its preparation method and application. The X-ray powder diffraction pattern of the new crystal form of fosfomycin sodium has characteristic peaks at the following 2θ angle positions: 6.59 ± 0.2°, 6.90 ± 0.2°, 15.88 ± 0.2°, 18.43 ± 0.2°, 18.72 ± 0.2°, 20.94 ± 0.2° and 30.65 ± 0.2°. Its preparation method includes: fosfomycin left phosphorus right amine salt is dissolved in sodium hydroxide aqueous solution, liquid separation, water layer is added to alcohol solvent and stirred for crystallization, filter cake is washed after filtration, filter cake is passed through saturated water nitrogen and purged to the filter cake surface to appear molten state, vacuum drying, obtains fosfomycin sodium new crystal form. Fosfomycin sodium provided by the present invention is a hemihydrate crystal form, and its hygroscopicity is low, which is more conducive to subpackaging and mixing in production.

This invention belongs to the technical field of medicinal chemistry, specifically relating to a novel crystal form of cariprazine, specifically the cariprazine-4-hydroxybenzoic acid-methanol-hemihydrate crystal form and its preparation method. The novel cariprazine-fumaric acid crystal form provided by this invention comprises a basic unit of one molecule of cariprazine, one molecule of 4-hydroxybenzoic acid, one molecule of methanol, and 0.5 molecules of water. Its preparation method is simple to operate, the crystallization process is easy to control, and it has good reproducibility. The formation of a eutectic significantly enhances the solubility of cariprazine, exhibiting strong pharmaceutical value.

The invention discloses an efficient retarding and strength-retaining composite retarding formula and application of the efficient retarding and strength-retaining composite retarding formula in alpha-semi-hydrated gypsum, and the composite retarding formula is prepared from the following raw materials in parts by weight: 0.01 to 0.06 part of sodium tripolyphosphate, 0.02 to 0.08 part of a retarding auxiliary agent and 0.01 to 0.04 part of a reinforcing agent; the retarding auxiliary agent is a composition of protein substances and carbohydrates. The composite retarding formula developed by the invention has a synergistic effect, aims to realize efficient retarding under a low mixing amount, meanwhile, the used raw materials are low in price and easy to obtain, the operation is simple and convenient, and the composite retarding formula shows a wide prospect for high-valued application of alpha-HH.

To provide a cement composition comprising Portland cement and hemihydrate gypsum, which can form a mortar hardened body having excellent dimensional stability in water and has excellent rapid hardening properties.SOLUTION: There is provided a cement composition comprising a hydraulic component composed of Portland cement and hemihydrate gypsum, a limestone fine aggregate, a carbonate, a water-reducing agent, a thickening agent and a defoaming agent. Based on the total amount of the hydraulic component, the content of the Portland cement is 20 to 60 mass% and the content of the hemihydrate gypsum is 40 to 80 mass%. The content of the limestone fine aggregate is 50 to 250 pts.mass and the content of the carbonate is 0.30 to 1.8 pts.mass, the content of the water-reducing agent is 0.03 to 6.0 pts.mass, the content of the thickening agent is 0.03 to 4.0 and the content of the defoaming agent is 0.03 to 4.0 pts.mass, based on 100 pts.mass of the hydraulic component.SELECTED DRAWING: None

The application provides a method for testing gypsum moisture content based on nuclear magnetic resonance, comprising the following steps: performing nuclear magnetic resonance test on a gypsum sample to be tested to obtain a nuclear magnetic resonance signal amplitude; the magnetic field strength of the nuclear magnetic resonance test is less than or equal to 1T; obtaining the mass of water in the gypsum sample according to a predetermined standard curve and the signal amplitude; obtaining the gypsum moisture content according to the mass of water in the gypsum sample and the mass of the gypsum sample to be tested; and the predetermined standard curve is a linear relationship curve of the mass of water in the gypsum and the signal amplitude. The application adopts a low-field nuclear magnetic resonance method (magnetic field strength less than or equal to 1T) to non-destructively determine the water content in the gypsum, thereby determining the type of the gypsum (anhydrite, hemihydrate gypsum and dihydrate gypsum). The method provided by the application does not need to dry the gypsum sample to be tested, has the advantages of rapidness and non-destructiveness, and has a wide application prospect in the determination of water content in the gypsum field and the determination of different types of gypsum.

The invention discloses a building exterior wall freeze-thaw crack repairing material, a building exterior wall material and a preparation method thereof, relates to the technical field of building materials, and solves the problem that freeze-thaw cracks are easy to appear in the existing building exterior wall in severe cold areas. The repairing material is prepared from butyl acrylate, glycidyl methacrylate, ethyl p-methoxycinnamate, PEG (Polyethylene Glycol)-S-S-PEG (Polyethylene Glycol), N-TiO2 (at) PANI (Polyaniline) composite particles, bacillus pasteurii microcapsules, nutritive salt microcapsules and a photoinitiator HMPP (Hydroxymethyl Propionic Acid). The building exterior wall material further comprises quartz sand, shale ceramsite, P.O 42.5 cement, beta-semi-hydrated gypsum powder, a polycarboxylic acid type water reducing agent, hydroxypropyl methyl cellulose, ethylene glycol, an organic silicon type defoaming agent, nano calcium carbonate and chopped cellulose fibers. The overall maintenance cost can be reduced, the structural safety is improved, and the requirements of northern buildings are met.

The application discloses a kind of phosphoric acid extraction semi-water-two water alternate crystallization system and method, belong to the technical field of wet-process phosphoric acid production, the system is by the reaction tank unit of series connection and semi-water and two water reaction tank alternate arrangement, with the sulfuric acid dilution mixed heat exchanger group connected with reaction tank, simple heat exchanger group is arranged between tank to realize heat transfer.Construction.The method includes: material is temperature-adjusted after passing through sulfuric acid dilution mixed heat exchanger, in turn into the reaction tank sequence of alternate arrangement, heat circulation is carried out in adjacent tank by simple heat exchanger, under the control of PLC in 75~85 DEG C and 88~95 DEG C interval, realize the alternate crystallization of semi-water-two water calcium sulfate.The application replaces traditional flash evaporation external discharge with heat internal circulation between tank, solves the technical problems of high steam energy consumption, low phosphorus recovery rate, insufficient phosphoric acid concentration and high upgrading cost of stock device in traditional process, and has the comprehensive advantages of energy saving, yield, low-cost transformation and phosphogypsum resource.

The invention discloses a self-leveling gypsum base plate. The self-leveling gypsum base plate comprises a base layer and a self-leveling layer, the base layer is prepared from 100 parts of building gypsum, 0.2 to 0.4 part of composite retarder, 0.3 to 0.7 part of high-performance polycarboxylic acid water reducing agent, 6 to 12 parts of mixed fiber and 15 to 25 parts of functional filler; the self-leveling layer is arranged on the upper surface of the base layer and comprises the following components in parts by weight: 80-120 parts of semi-hydrated gypsum, 2-6 parts of redispersible latex powder, 0.1-0.5 part of cellulose ether, 0.05-0.2 part of a defoaming agent, 0-5 parts of pigment and 30-60 parts of water. Meanwhile, the invention discloses production equipment of the gypsum base plate. The self-leveling gypsum base plate disclosed by the invention has good flatness, high strength and good durability; meanwhile, the production equipment can realize automatic production, improve the production efficiency, reduce the energy consumption, accurately control various parameters in the production process, and ensure the stability and consistency of the product quality.

The invention belongs to the technical field of additives for building materials, and particularly relates to a composite early strength agent as well as a preparation method and application thereof. The preparation method of the composite early strength agent provided by the invention comprises the following steps: 1) weighing raw materials including fly ash, semi-hydrated gypsum, carbide slag, triethanolamine, a polycarboxylate superplasticizer and water; 2) mixing fly ash, semi-hydrated gypsum and carbide slag, adding triethanolamine, and grinding to obtain ground powder; (3) mixing the ground powder obtained in the step (2) with water, heating and reacting to obtain reaction slurry; and 4) mixing the reaction slurry obtained in the step 3) with a polycarboxylate superplasticizer, and then grinding to obtain the composite early strength agent. When the composite early strength agent obtained by the specific method is added into a sodium sulfate excited slag system, the early strength of the system can be improved, and the effect of accelerating hydration in a cement-based material is achieved.

A method for producing phosphoric acid, comprising attack in an aqueous medium of phosphated rock with sulfuric acid, with formation of a first dihydrate slurry suspended in an aqueous phase having a free P2O5 content between 38 and 50% and a free SO3 content of less than 0.5%, conversion of this first slurry by heating with recrystallization of the solubilized calcium sulfate giving rise to a second hemihydrate slurry, and separation in the second slurry between a production phosphoric acid and a hemihydfate cake, characterized in that it comprises'during the attack, addition of a fluorine source in the first slurry in a content from 1 % to 5% by weight of F relatively to the P2O5 contained in the phosphated rock.

The invention provides a mesoporous gypsum block and a preparation method thereof, and relates to the technical field of building materials and novel wall materials, the mesoporous gypsum block is prepared from the following raw materials by weight: 35-65 parts of hemihydrate gypsum, 40-60 parts of anhydrous II gypsum, 1.5-2.5 parts of nano mesoporous silica or modified nano mesoporous silica, 0.1-0.15 part of a polycarboxylic acid water reducer, 2-5 parts of a fiber reinforced material, and 90-150 parts of water. According to the invention, nano mesoporous silica is selected as a hard template agent and is compounded with two kinds of biphase gypsum, i.e., semi-hydrated gypsum and anhydrous II gypsum, so that the mesoporous gypsum block is generated, and the mesoporous gypsum block has a relatively strong pore skeleton structure and relatively good thermal stability, and has more excellent heat insulation performance compared with a traditional heat insulation material; energy is saved, consumption is reduced, space is saved, auxiliary materials are saved, and the service life is long.

An underlayment material composition is disclosed that includes a binder, a filler, a polymer, and a retarder. The binder includes calcium sulphate alpha hemihydrate, the filler includes cork, the polymer includes superplasticizer, and the retarder includes modified amino acid. The underlayment material exhibits a thermal resistance value that exceeds a threshold value for a defined thickness value. Further, a method of using the underlayment material composition in non-structural applications of one or more construction-related activities includes mixing the underlayment material composition, that includes the binder, the filler, the polymer, and the retarder, with a defined amount of water for a defined amount of time to produce an underlayment material composition mix having a defined consistency. The method further includes applying a coat of the underlayment material composition mix on a primer-coated surface.

According to a first aspect, the invention relates to a process for the production, preferably continuous, of calcium sulfate alpha hemihydrate, the process comprising: - the preparation of an aqueous gypsum suspension comprising gypsum in particulate form, water and at least one superplasticizing polymer selected from phosphate polyethers, sulfonated melamine formaldehyde (SMF) and sodium poly(styrene sulfonate); - the calcination of the aqueous gypsum suspension at a suitable temperature and pressure to obtain a suspension of calcium sulfate alpha hemihydrate; - optionally, the filtration of the calcium sulfate alpha hemihydrate suspension to separately obtain a concentrated alpha hemihydrate suspension and an aqueous filtrate.The invention also relates, according to a second aspect, to a process for preparing a gypsum-based product comprising the preparation of a plaster suspension comprising calcium sulfate alpha hemihydrate obtained by the process according to the invention. Furthermore, the invention relates to a plaster-based product obtained using a process according to the invention. The invention also relates to a gypsum-based product obtained using a process according to the invention, such as a plasterboard. Figure 2.

The application discloses a kind of phosphogypsum solid waste's step-by-step modification calcination preparation method, belong to solid waste treatment technical field.The method includes: (1) pre-coating treatment: the original state of containing attached water dihydrate phosphogypsum is mixed with composite modifier and is ground, and pre-coated phosphogypsum is obtained;(2) temperature control calcination: the pre-coated phosphogypsum obtained in step (1) is sent into calcining kiln, and dehydration reaction is carried out at 165 DEG C~180 DEG C temperature, and hemihydrate gypsum powder is obtained;(3) hygroscopic aging: the hemihydrate gypsum powder obtained in step (2) is cooled and aged 24h~48h, and the components in powder are used to absorb moisture in air to carry out hydration reaction, and the final product is obtained.The method is free of water washing, short process, and the obtained phosphorus building gypsum standard consistency water consumption is 45%~50%, and 2 hour compressive strength is greater than or equal to 6.5MPa.

This invention discloses a method for purifying and classifying low-quality, compacted phosphogypsum to prepare building materials, comprising the following steps: 1) feeding low-quality, compacted phosphogypsum into a ceramic ball mill for grinding to obtain phosphogypsum slurry; 2) feeding the phosphogypsum slurry into an ultrasonic cleaner for ultrasonic vibration cleaning; 3) obtaining a foam product as high-silica tailings and an underflow product as high-purity phosphogypsum slurry; 4) feeding the high-silica tailings into a filter for filtration, and then adding fly ash and an alkali activator to the filtered high-silica tailings to obtain a phosphogypsum-based polymer; 5) filtering the high-purity phosphogypsum slurry through a filter, drying it in an oven, and finally calcining it in a calcining furnace to obtain high-quality β-hemihydrate gypsum powder. This invention is simple and feasible, and particularly effective in purifying low-quality phosphogypsum with many impurities and severe compaction, without generating secondary solid waste. It also provides a reasonable and reliable full-scale application technology route for the resource utilization of low-quality, compacted phosphogypsum.

The present invention, when gypsum particles derived from waste gypsum boards are calcined using a hot-air rotary calcinator, makes the calcined gypsum particles have a reduced gypsum dihydrate content. Gypsum particles obtained by crushing waste gypsum boards and made of gypsum dihydrate are calcined. The gypsum particles are supplied to a cylindrical rotating tank, and the gypsum particles are stirred by the rotation of the tank. Hot air is supplied to a pipe positioned at the axial-direction center of the tank and provided with a plurality of nozzles, and is blown from the nozzles into the gypsum particles, thereby converting the gypsum dihydrate in the gypsum particles into gypsum hemihydrate and / or III-form anhydrous gypsum. The peripheral speed of the inner wall of the rotating tank is in the range of 2-10 m / min.　

The invention relates to the technical field of ardealite retarders, in particular to an alpha-like fresh semi-hydrated ardealite retarder, which is prepared from the following raw materials in percentage by mass: 96 to 98 percent of fresh semi-hydrated ardealite and 2 to 4 percent of functional additive, the preparation method comprises the step of uniformly mixing the fresh semi-hydrated phosphogypsum and the functional additive. The alpha-type fresh semi-hydrated phosphogypsum is used as a main raw material, the retarding time is controlled by adjusting the mixing amount of sodium phosphate and tartaric acid, the retarding requirements of different types of cement can be met, and the application is wide; moreover, the retarder also has the characteristics of wide source, small additive dosage, simple preparation process, reinforcement modification on cement in the aspects of freezing resistance, water resistance and moisture resistance, and the like, and is beneficial to reducing the production cost.