A method for preparing environment-friendly process stone by harmless solidification of industrial waste gypsum

Abstract

A kind of method for harmless solidification of industrial waste gypsum to environment-friendly process stone, comprising the following steps: S1, wet industrial waste gypsum is placed with alkalization water-retaining agent in mechanical mixing device, is stirred uniformly, and alkaline water-retaining gypsum material is obtained;S2, water-hardening cementing material, heavy metal solidification hydrophobic agent are added in the alkaline water-retaining gypsum material obtained in step S1, and continuously stirred and mixed uniformly, and sent into process stone moulding press forming machine to be pressed into process stone, and cured at room temperature or humid heat curing or dry steam curing for appropriate time, and finished product is obtained.The present application has simple process, no secondary pollution, low investment, large processing capacity for wet-state phosphogypsum and desulfurization gypsum harmless resource utilization, low operating cost, can effectively solve the serious pollution problem of phosphogypsum and desulfurization gypsum to environment and soil for a long time, and the product can meet the demand of environment-friendly artificial process stone for outdoor engineering such as municipal gardens, engineering rivers, ditches, road repair and slope protection.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for resource utilization of solid waste residues, in particular to a method for manufacturing environment-friendly process stone with good water resistance, salt corrosion resistance and durability by harmless solidification treatment of industrial waste gypsum, phosphogypsum and desulfurization gypsum. BACKGROUND

[0002] Phosphogypsum is an acid leaching solid waste residue discharged by phosphorus chemical industry in the process of producing phosphoric acid or phosphate fertilizer by wet method. Newly discharged phosphogypsum is acidic, mostly in the form of granular material with fine particle size, generally 5-50 μm, and the free water content is generally 10-25%, and the crystal water content is mostly 18%-20%. The main mineral component is crystalline gypsum grain, accounting for about 78-96%; the second is about 4-22% of quartz SiO2 and silicate minerals and insoluble phosphates, fluorophosphates which are not completely reacted in the acid leaching reaction, and a certain amount of soluble sulfates, phosphates and fluorophosphates, including a small amount of soluble salts of heavy metal elements such as arsenic, copper, zinc, iron, manganese, lead, cadmium and mercury, and some phosphogypsum also contains radioactive elements. Since phosphogypsum contains soluble heavy metal salts, improper disposal will pollute the environment and soil.

[0003] At present, the stockpiled amount of phosphogypsum in China is more than 600 million tons, and the annual production is more than 80 million tons. The production of phosphogypsum in Hubei, Yunnan, Guizhou and Sichuan, which account for about 73% of the total production in China, is large, and there is almost no suitable area for stockpiling. The pollution of phosphogypsum to the environment and soil and the difficulty in disposal and consumption have restricted the development of the phosphorus chemical industry.

[0004] In order to solve the disposal problem of phosphogypsum in the phosphorus chemical industry, a large number of scientific research institutions and all phosphorus chemical enterprises at home and abroad have carried out long-term research and practice on the disposal of phosphogypsum. The existing research and application technology of phosphogypsum can be roughly summarized as follows:

[0005] The first type is to use phosphogypsum to modify and replace natural gypsum as a cement retarder, that is, to neutralize the acidity of phosphogypsum with lime and use it as a cement retarder. However, the application effect is not ideal, and the actual consumption is very limited.

[0006] The second type is to use phosphogypsum as a sulfate activator and low-grade cementing material and product. For example, phosphogypsum is mixed with lime and coal ash or fly ash or slag, ground and made into low-grade masonry cement or mixed and pressed to make bricks after curing. However, due to the influence of harmful impurities and harmful elements and the limitation of application, the popularization and application of this method are not ideal.

[0007] The third type is to use phosphogypsum to produce a hard-bonded cementitious material, i.e. the phosphogypsum is modified, such as neutralized with lime, washed with water to remove salt, and then modified by steaming or autoclaving at 120-250°C to form α-type hemihydrate gypsum which is finely ground to produce high-strength gypsum powder, or the phosphogypsum is washed with water to remove salt and then dehydrated by heat treatment at 170-500°C to produce β-type hemihydrate + anhydrite gypsum building gypsum powder, which is used to produce gypsum putty, gypsum molds, and gypsum board, gypsum blocks and other gypsum products; or the phosphogypsum is dehydrated by heat treatment at a high temperature of 500-900°C to produce anhydrite cementitious material and products such as anhydrite self-leveling material, but due to the grade and color of the phosphogypsum and the presence of a certain amount of harmful elements and impurities, the actual application market is small, and the consumption of phosphogypsum is limited.

[0008] The fourth type is to use phosphogypsum to produce a gypsum filler, i.e. the phosphogypsum is heat-treated and superfine ground with a silane coupling agent to produce an anhydrite filler, which is used in the production of plastic products.

[0009] The fifth type is to use phosphogypsum to produce gypsum whiskers, i.e. the phosphogypsum is dissolved in a large amount of water to control recrystallization into needle-shaped gypsum whiskers, which are used in the production of plastic products.

[0010] The sixth type is to use phosphogypsum to produce special cement, i.e. to replace natural gypsum to produce sulphoaluminate cement, ferrosulphate cement, belite-anhydrite cement, high-sulphur cement or fluoroaluminate cement, etc. This type of technology requires high-temperature heat treatment of phosphogypsum at above 1200°C, which has high energy consumption, and if the process parameters are not properly controlled and disposed of, it is difficult to stably meet the environmental protection emission standards, and it is difficult to land in the market for replacing the oversaturated silicate cement.

[0011] The seventh type is to use phosphogypsum to produce by-product cement for sulphuric acid production, which has large investment, low sulphuric acid grade, poor economy, and large secondary pollution, which hinders its popularization and application.

[0012] The eighth type is to use phosphogypsum to backfill a mine, i.e. to directly backfill or mix and pump backfill a mine with hot acid leaching hemihydrate phosphogypsum or lime, or to backfill a mine with hemihydrate gypsum produced by heat treatment of phosphogypsum, because the structure of the material after backfilling the mine is loose and porous, the soluble salts of heavy metals cannot be effectively solidified, and objectively it is a way of transferring pollutants out of sight.

[0013] The ninth type is to modify phosphogypsum as roadbed material. For example, CN 202210207971.8 discloses a preparation method of high-plastic modified thin slurry seal coating road material, and CN 202111560448.5 discloses an industrial solid waste curing agent and a preparation method thereof. The method is to mix phosphogypsum with a small amount of cement and a curing agent, and then use a road roller to compact the mixture as a roadbed material. It should be considered that this is the most advanced method for the resource utilization of phosphogypsum. Theoretically, this method is feasible, but in practical application, it has the following two defects: first, the process determines that it is difficult to effectively coat and solidify the soluble salts of heavy metals; second, it is difficult to fully compact and solidify with a road roller, and there are structural porous and loose problems, and there are arching and cracking self-destruction problems, which are actually still a way of transferring pollutants; more seriously, the late reactivity damage to the concrete layer engineering will harden the nearby farmland.

[0014] The tenth type is to directly replace sulfur trioxide with phosphogypsum. This method is to replace sulfur trioxide in stripped gypsum with siliceous material under specific conditions, and the application conditions are harsh.

[0015] Due to the limited market of existing comprehensive utilization methods and products of phosphogypsum, under the condition of government subsidies for the disposal of phosphogypsum (5000 million yuan per 100 million tons / a) and subsidies of 100-140 yuan per ton of phosphogypsum for phosphorus chemical enterprises, phosphogypsum still has to be stored in a warehouse or disposed by backfilling pollutants, and accidents of water and soil pollution and ecological pollution caused by phosphogypsum still occur, so there is an urgent need for a new resource utilization and harmless treatment idea.

[0016] In addition to phosphorus gypsum, another kind of large industrial waste gypsum, desulfurization gypsum, also known as flue gas desulfurization gypsum, sulfur gypsum or FGD gypsum, due to its fine particles (average particle size about 40um-60um, particle is short columnar, diameter length ratio between 1.5-2.5), containing free water generally in 10%-25%, crystal water generally in 18%-21%, its main component is gypsum (CaSO4·2H2O content generally ≥93%) and about 1%-7% of unreacted calcium carbonate, and contains about 1% of fly ash, organic carbon and calcium sulfite and sodium, potassium, magnesium, zinc, lead, cadmium, mercury and other sulfates, sulfites, chlorides, acid carbonates and other soluble salts and other impurities, the current storage or landfill has caused significant groundwater and ecological environment pollution problems. The existing desulfurization gypsum treatment method is similar to the resource utilization scheme of phosphorus gypsum, although the water washing desulfurization gypsum, heat treatment for building gypsum powder for gypsum board, block and other aspects have made important achievements, but the disposal amount of desulfurization gypsum is still limited, and the disposal subsidy of desulfurization gypsum in some areas is more than 100 yuan per ton, the accumulation amount of desulfurization gypsum is still increasing year by year, and a large amount of desulfurization gypsum is simply buried, which has a great impact on the surface water, especially the groundwater, the ecological environment and even the health of people.

[0017] Therefore, the harmless resource utilization of large industrial waste slag, phosphorus gypsum and desulfurization gypsum, urgently needs a new technical idea and technical scheme, especially how to convert industrial waste gypsum into an environmentally friendly material by an energy-saving process.

[0018] On the other hand, the landscape and engineering construction of towns and villages in China need a large amount of process stone building materials which are resistant to water, salt erosion and weathering. At present, the process stone needed depends on the exploitation of natural limestone, granite and other natural stones, which not only destroys the natural environment, but also makes the process stone expensive and leads to high engineering cost. SUMMARY

[0019] The technical problem to be solved by the present application is to overcome the above-mentioned defects of the prior art, and to provide a method for harmless solidification of industrial waste gypsum to prepare environmentally friendly process stone. The method can convert the phosphorus gypsum and desulfurization gypsum which has been continuously polluting the groundwater and downstream water environment for a long time due to storage, landfill and flushing treatment into economically good and environmentally friendly process stone building materials needed for landscape beautification and engineering. The prepared process stone is hydrophobic, resistant to water, salt erosion and weathering.

[0020] The technical scheme adopted by the present application to solve the technical problem is: a method for harmless solidification of industrial waste gypsum to prepare environmentally friendly process stone, comprising the following steps:

[0021] S1, solidification of soluble salt alkalization water-retaining treatment: wet industrial waste gypsum and alkalization water-retaining agent are placed in a mechanical mixing device, and continuously stirred for 3-60 minutes to convert soluble sulfates, phosphates, fluorophosphates adhered to the surface of crystalline waste gypsum particles and free soluble salts in waste gypsum into insoluble or hardly soluble calcium sulfate, calcium phosphate, calcium fluorophosphate, and to convert soluble heavy metal ions into hydroxides that are easily combined with silicate and aluminate groups, and to make the mixture alkaline, to obtain alkaline water-retaining gypsum material;

[0022] The alkalization water-retaining agent is a substance that can react with water-soluble sulfates, fluorophosphates, etc. to generate insoluble or hardly soluble minerals under aqueous conditions.

[0023] S2, modification of environment-friendly process stone: under continuous stirring, water-hardening binder and heavy metal solidification hydrophobic agent are added to the alkaline water-retaining gypsum material obtained in step S1 at a mass ratio of 100:5-28:0.5-8, and continuously stirred for 2-30 minutes to obtain a mixture, which is then sent to a process stone molding machine to be pressed into process stone, and naturally cured at room temperature above 20℃ for more than 7 days, or wet-heat cured at 50-98℃ for more than 24 hours, or dry-steam cured at 40-98℃ for more than 24 hours, to obtain waste gypsum environment-friendly process stone with water resistance, salt corrosion resistance and weathering resistance.

[0024] The heavy metal solidification hydrophobic agent is a substance that can react with heavy metal ions such as zinc, lead, cadmium, mercury, manganese, copper and chromium in industrial waste gypsum and its hydroxides to form insoluble minerals and have hydrophobic characteristics. The heavy metal solidification hydrophobic agent mainly contains active silicate groups and / or aluminate groups and / or silico-aluminate groups, which can solidify and coat heavy metal ions in waste gypsum and make them hydrophobic.

[0025] The waste gypsum environment-friendly process stone or environment-friendly process stone is a decorative or culturally characteristic product made of phosphogypsum / desulfurization gypsum as raw material by harmless water-hardening and hydrophobic solidification, which can be used for outdoor engineering such as municipal garden river, ditch, road repair and slope protection, and has good water resistance, salt corrosion resistance and durability.

[0026] Further, in step S1, the substance that can react with water-soluble sulfates, fluorophosphates, etc. to generate insoluble or hardly soluble minerals under aqueous conditions is preferably at least one of high-calcium fly ash, carbide slag, lime slag powder, lime powder, calcined dolomite powder, methyl cellulose, carboxymethyl cellulose, hydroxyethyl / hydroxypropyl cellulose, sodium alginate, and superabsorbent resin.

[0027] Further, in step S1, the amount of alkaliizing water-retaining agent is 1.0% to 19.8% of the mass of the wet industrial waste gypsum, and the specific ratio is selected according to the content of soluble salts such as sulfates and fluorophosphates and the moisture content in the wet industrial waste gypsum. When the content of soluble salts in the wet waste gypsum is high and the moisture content is high, the upper limit is taken.

[0028] Further, in step S1, the wet waste gypsum refers to fresh phosphogypsum or desulfurization gypsum with a moisture content of 6% to 32%, or phosphogypsum or desulfurization gypsum with a moisture content of less than 32% stored in a slag pool or a slag storage, or phosphogypsum or desulfurization gypsum that has been dried, crushed, and then wetted with an appropriate amount of water.

[0029] Further, in step S1, the alkalinity is pH≥12.

[0030] Further, in step S2, the hydraulic cementing material is at least one of Portland cement, aluminate cement, sulfoaluminate cement, double-quick cement, and slag and fly ash active slag powder.

[0031] Further, in step S2, during the stirring process, semi-hydrated or anhydrous gypsum (anhydrite) powder, building sand and gravel aggregates, waste concrete granular materials, tailings sand, or other industrial waste residues that do not produce antagonistic destructive effects can also be added.

[0032] Further, in step S2, during the molding process, reinforcing ribs or nets can be laid, and / or drainage or wiring pipes can be pre-installed.

[0033] Further, in step S2, the environment-friendly process stone produced can be further subjected to impregnation and / or waterproofing treatment.

[0034] Further, in step S2, the environment-friendly process stone produced can be further subjected to decorative spraying and / or polishing treatment.

[0035] The present application is based on the mineral composition characteristics and particle size distribution characteristics of the waste residue of phosphogypsum discharged in the process of producing phosphoric acid from acid-leached phosphate rock powder, and the mineral composition characteristics and particle size distribution characteristics of the waste residue of desulfurization gypsum produced in the limestone powder wet flue gas desulfurization process of a thermal power plant, as well as the distribution characteristics of harmful substances. Under the condition of containing water, the alkalinizing water-retaining agent converts the soluble sulfates, phosphates, and fluorophosphates in the phosphogypsum into insoluble or hardly soluble calcium sulfate, calcium phosphate, and calcium fluorophosphate, or converts the soluble sulfates, sulfites, chlorides, and acid carbonates in the desulfurization gypsum into insoluble or hardly soluble calcium sulfate, calcium carbonate, and calcium chloroaluminate / sulfoaluminate. At the same time, the soluble heavy metal ions are converted into hydroxides that are easy to combine with silico-aluminate groups, and the mixture is kept alkaline, in a state similar to the activation of sulfur alkali activator, to facilitate the induction of dihydrate gypsum activation recrystallization and water-hardening compound coating to form water-hardening hydrophobic curing conditions. Then, the water-hardening cementitious materials and heavy metal solidification hydrophobic agents are added in proportion, stirred and mixed uniformly, sent to a process stone molding machine for pressing into process stone, and then cured to form water-hardening hydrophobic curing process stone, completely eliminating the hazards of soluble heavy metals and soluble salts in wet-state phosphogypsum and desulfurization gypsum and stabilizing and solidifying them. The molded product is an environmentally friendly artificial stone product with hydrophobic, water-resistant, and salt-resistant corrosion resistance and durability, and can be used as a cultural heritage or decorative effect. It can meet the needs of municipal gardens, engineering river ditches, road repair and slope protection, and other outdoor engineering for environmentally friendly artificial stone with water-resistant, salt-resistant, and weather-resistant properties.

[0036] The beneficial effects of the present application are: 1. The process is simple, without secondary pollution; the investment is relatively low, and the treatment capacity of the harmless resource utilization of the wet-state phosphogypsum and desulfurization gypsum is large, the operating cost is relatively low, the potential market demand of the environment-friendly hydrophobic and water-resistant and salt-erosion-resistant and weathering-resistant process stone product is large; 2. In the present application, under the condition of the water content of the wet-state phosphogypsum and desulfurization gypsum, the alkaliizing water-retaining agent is used to convert the soluble sulfate, phosphate, fluorophosphate and the like in the phosphogypsum into insoluble or hardly soluble calcium sulfate, calcium phosphate, calcium fluorophosphate / calcium fluoride and the like, or the alkaliizing water-retaining agent is used to convert the soluble sulfate, sulfite, chloride, acid carbonate in the desulfurization gypsum into insoluble or hardly soluble calcium sulfate, calcium carbonate, calcium chloroaluminate / calcium sulphoaluminate, at the same time, the soluble heavy metal ions are converted into hydroxides which are easy to form silicoaluminate groups, and the mixture is kept alkaline, in a state similar to the activation of sulfur alkali activator, which is conducive to inducing the activation recrystallization of dihydrate gypsum and the water-hardening coating, and the water-hardening hydrophobic curing conditions can be formed, and the water-hardening cementitious material, heavy metal solidification hydrophobic agent and the like are compounded, and the process stone is pressed and cured by a process stone molding machine to form a water-hardening hydrophobic curing process stone, which completely eliminates the harm of the soluble heavy metal ions and soluble salts in the wet-state phosphogypsum and desulfurization gypsum and stabilizes and solidifies them, realizes the complete harmless resource utilization of the phosphogypsum and desulfurization gypsum with low energy consumption and without secondary pollution, and effectively solves the serious pollution problem of the phosphogypsum and desulfurization gypsum to the environment and soil for a long time; 3. The environment-friendly artificial process stone product with the ability of hydrophobicity, water resistance and salt erosion resistance and durability and with cultural connotation or decorative effect can be made by molding, which can meet the demand of the environment-friendly artificial process stone for water resistance, salt erosion resistance and weathering resistance in outdoor engineering such as municipal gardens, engineering rivers, ditches, road repair and slope protection, and the like, can provide cheap and high-quality process stone building materials for the beautification of municipal, county and rural gardens and engineering, is conducive to the implementation of national ecological restoration, and is conducive to the construction of local cultural characteristics and the promotion of local humanistic characteristics and tourism landscape. DETAILED DESCRIPTION

[0037] The present application is further described below in combination with examples.

[0038] The raw material components used in each embodiment and the performance testing of the artificial craft stone products prepared are carried out according to the following standard testing methods and specifications: “Solid Waste Leaching Toxicity Leaching Method Horizontal Oscillation Method” (HJ 557-2010), “Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid Nitric Acid Method” (HJ / T 299-2007), “Solid Waste Determination of Lead, Zinc and Cadmium Flame Atomic Absorption Spectrophotometry” (HJ 786-2016), “Hazardous Waste Identification Standard Leaching Toxicity Identification Appendix B Solid Waste Determination of Elements Inductively Coupled Plasma Mass Spectrometry” (GB 5085.3-2007), “Solid Waste Determination of Mercury, Arsenic, Selenium, Bismuth, Antimony Microwave Digestion / Atomic Fluorescence Method” (HJ 702-2014), “Solid Waste Leaching Toxicity Determination Method” (GB / T 15555.1~12-1995), “Technical Specification for Co-processing of Solid Waste in Cement Kilns” (GB / T 30760-2014), “Standard for Test Methods of Properties of Ordinary Concrete Mixtures” (GB / T 50080-2016), “Standard for Test Methods of Physical and Mechanical Properties of Ordinary Concrete” (GB / T 50081-2019), “Standard for Test Methods of Long-term Properties and Durability of Ordinary Concrete” (GB / T 50082-2009), “Standard for Building Concrete and Precast Products” (JGJ / T 70-2009), “Standard for Durability Design of Concrete Structures” (GB / T 50476-2019), “Limit of Radioactive Nuclides in Building Materials” (GB 6566-2010), “Specification for Treatment and Disposal of Phosphogypsum” (GB / T 32124). Example 1

[0039] The wet industrial waste gypsum used in this embodiment is fresh phosphogypsum waste slag discharged from the process of producing phosphoric acid from acid-leached phosphate rock powder, with a moisture content of 15.3% and a soluble salt content of 1.79%; the alkalizing water-retaining agent used in the experiment is a substance that can react with water-soluble sulfates, fluorophosphates, etc. under water-containing conditions to form insoluble or poorly soluble minerals, and commercially available calcined dolomite powder and carboxymethyl cellulose are selected for addition at a mass ratio of 100:1, with the alkaline water-retaining agent being 5.8% of the wet phosphogypsum waste slag; the hydraulic cementitious material is a commercially available aluminates cement; the heavy metal solidification hydrophobic agent is a compound of commercially available water-soluble sodium silicate and water-soluble epoxy resin at a mass ratio of 30:1; the water-resistant and salt-resistant industrial waste gypsum environment-friendly craft stone is manufactured according to the following steps:

[0040] S1, solidification of soluble salt-alkalization water-retaining treatment: wet industrial waste gypsum and alkalization water-retaining agent are placed in a mechanical mixing device, and continuously stirred for 20 min, so that soluble sulfates / sulfites, phosphates, fluorophosphates adhered to the surface of crystalline waste gypsum particles and free soluble salts in waste gypsum are converted into insoluble or hardly soluble calcium sulfate, calcium phosphate, calcium fluorophosphate, and soluble heavy metal ions are converted into hydroxides which are easily combined with silicate and aluminate radicals, and the mixture is alkaline (pH 12), to obtain alkaline water-retaining gypsum material;

[0041] S2, modification of environment-friendly process stone: under continuous stirring, the alkaline water-retaining gypsum material obtained in step S1 is mixed with hydraulic cementing material and heavy metal solidification hydrophobic agent in a mass ratio of 100:12.2:1.1, and continuously stirred for 10 min to obtain a mixture, which is then sent to a process stone molding machine to be pressed into a dragon-shaped process stone, and naturally cured at room temperature above 20℃ for 14 days to obtain an environment-friendly process stone which is resistant to water, salt corrosion and weathering, and has good volume stability, high strength and durability of more than 50 years. The results of various experimental tests are as follows:

[0042] 1, leaching toxicity test results

[0043]

[0044] 2, mechanical property test results

[0045]

[0046] water absorption 0.6%;

[0047] softening coefficient 0.87;

[0048] 3, durability test results

[0049] frost resistance test: after 46 freeze-thaw cycles, there is no obvious damage and peeling;

[0050] water permeability coefficient 3.7*10 -8 m / s;

[0051] chloride ion diffusion coefficient 52*10 -14 m 2 / s;

[0052] linear drying shrinkage value 0.008%;

[0053] The test results of this batch show that the process stone with dragon totem has good water resistance, salt corrosion resistance and aging resistance, good volume stability, high strength and durability of more than 50 years. The toxicity leaching test and radioactivity test show that the product is harmless and meets the requirements of environment-friendly materials, and is an environment-friendly process stone made of industrial waste gypsum. Example 2

[0054] The raw material used in this example is wet industrial waste gypsum obtained from a flue gas desulfurization process in a power plant. The water content is 12.8%, and the soluble salt content is about 0.9%. The alkalizing water-retaining agent used in the experiment is commercially available lime powder and superabsorbent resin, added in a mass ratio of 80:1, with a dosage of 4.9% of the mass of the desulfurization gypsum. The hydraulic cementitious material is commercially available Portland cement. The heavy metal solidification and hydrophobic agent is a compound of commercially available potassium meta-aluminate and water-soluble epoxy resin in a mass ratio of 30:1. The environmentally friendly water-resistant and salt-resistant industrial waste gypsum process stone is manufactured according to the following steps:

[0055] S1, solidification of soluble salt alkalization and water retention treatment: wet industrial waste gypsum and alkalization water-retaining agent are placed in a mechanical mixing device and continuously stirred for 30 minutes. The soluble sulfate / sulfite, phosphate, fluorophosphate adhering to the surface of the crystalline waste gypsum particles and the free soluble salt in the waste gypsum are converted into insoluble or hardly soluble calcium sulfate, calcium phosphate, and calcium fluorophosphate. At the same time, the soluble heavy metal ions are converted into hydroxides that are easily combined with silicate and aluminate groups, and the mixture becomes alkaline (pH value 12.3), obtaining alkaline water-retaining gypsum material;

[0056] S2, modification of environmentally friendly process stone: under continuous stirring, the alkaline water-retaining gypsum material obtained in step S1 is added with hydraulic cementitious material and heavy metal solidification and hydrophobic agent in a mass ratio of 100:9.2:0.9 of phosphogypsum or desulfurization gypsum, hydraulic cementitious material, and heavy metal solidification and hydrophobic agent. After continuous stirring for 15 minutes, the mixture is uniformly mixed and sent to a process stone molding machine to be pressed into process stone with white tiger characteristics. After wet heat curing at 50-60°C for 48 hours, the water-resistant, salt-resistant, and weather-resistant environmentally friendly process stone is obtained. The experimental detection results are as follows:

[0057] 1. Leaching toxicity test results

[0058]

[0059] 2. Mechanical property test results

[0060]

[0061] Water absorption rate 0.7%;

[0062] Softening coefficient 0.86;

[0063] 3. Durability test results

[0064] Freezing resistance test: after 45 freeze-thaw cycles, there is no obvious damage and peeling;

[0065] Water permeability coefficient 4.1*10 -8 m / s;

[0066] Chloride diffusion coefficient 54*10 -14 m 2 / s;

[0067] Linear drying shrinkage 0.007%;

[0068] The test results of this batch show that the white tiger totem process stone has good water resistance, salt corrosion resistance, and aging resistance, good volume stability, high strength, durability of more than 50 years, and non-hazardous product in the toxicity leaching test, meeting the requirements of environmentally friendly materials. It is an environmentally friendly process stone for industrial waste gypsum. Example 3

[0069] The wet industrial waste gypsum used in this example was taken from a stockpile in a certain place, with a moisture content of 20.1% and a soluble salt content of 1.75%. The alkaline water-retaining agent used in the experiment was commercially available high-calcium fly ash and carboxymethyl cellulose, added in a mass ratio of 100:1. The alkaline water-retaining agent was 12.1% of the wet-state phosphogypsum waste residue. The hydraulic cementitious material was commercially available sulphoaluminate cement. The heavy metal solidification and hydrophobic agent was a compound of commercially available potassium meta-aluminate and water-soluble acrylic resin in a mass ratio of 30:1. The environmentally friendly water-resistant and salt-resistant industrial waste gypsum process stone was manufactured according to the following steps:

[0070] S1, solidification of soluble salt alkalization and water retention treatment: The wet industrial waste gypsum and the alkalization water-retaining agent were placed in a mechanical mixing device and continuously stirred for 30 minutes. The soluble sulphate / sulphite, phosphate, fluorophosphate on the surface of the crystalline waste gypsum particles and the free soluble salt in the waste gypsum were converted into insoluble or slightly soluble calcium sulphate, calcium phosphate, calcium fluorophosphate / fluoride. At the same time, the soluble heavy metal ions were converted into hydroxides that were easily combined with silicon and aluminate groups, and the mixture became alkaline (pH 12.5). The alkaline water-retaining gypsum material was obtained.

[0071] S2, modification of environmentally friendly process stone: Under continuous stirring, the alkaline water-retaining gypsum material obtained in step S1 was added with hydraulic cementitious material, heavy metal solidification and hydrophobic agent, and building sand and gravel aggregate in a mass ratio of 100:15.2:1.1:7.3. The mixture was continuously stirred for 10 minutes and then sent to a process stone molding machine to press into a larger process stone with a purple imprint. The process stone was naturally cured at room temperature above 20°C for 28 days to obtain a water-resistant, salt-resistant, and weather-resistant environmentally friendly process stone. The results of various experimental tests are as follows:

[0072] 1. Toxicity detection results

[0073]

[0074] 2. Mechanical property test results

[0075]

[0076] Water absorption 0.5%;

[0077] Softening coefficient 0.88;

[0078] 3. Durability test results

[0079] Frost resistance test: no obvious damage and peeling after 48 freeze-thaw cycles;

[0080] Water permeability coefficient 3.2*10 -8 m / s;

[0081] Chloride ion diffusion coefficient 49*10 -14 m 2 / s;

[0082] Linear drying shrinkage value 0.008%;

[0083] The test results of this batch show that the process stone with redbud imprint has good water resistance, salt corrosion resistance and aging resistance, good volume stability, high strength, durability of more than 50 years, and is a harmless product and a environmentally friendly material, which meets the requirements of environmentally friendly materials. Example 4

[0084] The wet industrial waste gypsum used in this example is phosphogypsum obtained from a stockpile in a certain place, which is crushed and wetted with an appropriate amount of water. The water content is 18.2%, and the soluble salt content is 1.8%. The alkaline water-retaining agent used in the experiment is commercially available lime slag powder and methyl cellulose, which are added in a mass ratio of 120:1. The alkaline water-retaining agent is 10.2% of the wet phosphogypsum waste residue. The hydraulic cementitious material is commercially available double-quick cement. The heavy metal solidification and hydrophobic agent is a compound of commercially available sodium metaaluminate and water-soluble silicone oil in a mass ratio of 30:1. The water-resistant and salt-resistant industrial waste gypsum environmentally friendly process stone is manufactured according to the following steps:

[0085] S1, solidification and alkalization of soluble salt water-retaining treatment: the wet industrial waste gypsum and the alkalization water-retaining agent are placed in a mechanical mixing device and continuously stirred for 12 minutes. The soluble sulfates, sulfites, phosphates, fluorophosphates adhering to the surface of the crystalline waste gypsum particles and the free soluble salts in the waste gypsum are converted into calcium sulfate, calcium phosphate and calcium fluorophosphate, which are difficult to dissolve or insoluble. At the same time, the soluble heavy metal ions are converted into hydroxides that are easily combined with aluminate groups, and the mixture becomes alkaline (pH value 12.6), obtaining alkaline water-retaining gypsum material;

[0086] S2, modifying the environment-friendly process stone: under continuous stirring, the basic water-retaining gypsum material obtained in step S1 is added with water-hardening cementing material and heavy metal solidification hydrophobic agent in a mass ratio of 100:13.2:1.2, and continuously stirred for 10 min, mixed uniformly, and sent into a process stone molding machine to be pressed into a purple king imprint process stone, which is dry steamed and cured at 65-75°C for 48 h to obtain a water-resistant, salt-resistant, weather-resistant, and environment-friendly process stone. The experimental results are as follows:

[0087] 1. Leaching toxicity test results

[0088]

[0089] 2. Mechanical property test results

[0090]

[0091] Water absorption rate 0.7%;

[0092] Softening coefficient 0.87;

[0093] 3. Durability test results

[0094] Freezing resistance test: no obvious damage and peeling after 46 freeze-thaw cycles;

[0095] Water permeability coefficient 4.2*10 -8 m / s;

[0096] Chloride ion diffusion coefficient 53*10 -14 m 2 / s;

[0097] Linear drying shrinkage value 0.009%;

[0098] The test results of this batch show that the process stone with purple king imprint has good water resistance, salt corrosion resistance, and aging resistance, good volume stability, high strength, and durability of more than 50 years. The toxicity leaching test and radioactivity test show that it is a harmless product, meeting the requirements of environment-friendly materials, and is an environment-friendly process stone of industrial waste gypsum. Example 5

[0099] The raw material of the embodiment is the industrial waste gypsum in wet state, which is the desulfurization gypsum stored in a certain place. The water content is 12.2%, and the soluble salt content is 0.9%. The alkalization water-retaining agent used in the experiment is the calcium carbide slag powder and hydroxypropyl cellulose purchased in the market, which are added in the proportion of 150:1. The alkalization water-retaining agent is 8.8% of the wet state phosphogypsum waste residue. The hydraulic cementitious material is the active slag powder of coal ash. The heavy metal solidification and hydrophobic agent is the compound of the commercially available potassium methyl silicate and silane coupling agent in the mass ratio of 20:1. The environment-friendly anti-water and anti-salt erosion industrial waste gypsum process stone is manufactured according to the following steps:

[0100] S1, solidification of soluble salt alkalization water-retaining treatment: the wet state industrial waste gypsum and the alkalization water-retaining agent are placed in a mechanical mixing device, and continuously stirred for 18 min. The soluble sulfate / sulfite, phosphate, fluorophosphate adhered to the surface of the crystalline waste gypsum particles and the free soluble salt in the waste gypsum are converted into calcium sulfate, calcium phosphate and calcium fluorophosphate, which are difficult to dissolve or insoluble. At the same time, the soluble heavy metal ions are converted into hydroxides which are easy to be combined with silicate groups, and the mixture is alkaline (pH value is 12.7), obtaining the alkaline water-retaining gypsum material;

[0101] S2, modification of environment-friendly process stone: under continuous stirring, the alkaline water-retaining gypsum material obtained in step S1 is added with the hydraulic cementitious material, heavy metal solidification and hydrophobic agent, and tailings sand in the mass ratio of 100:8.2:0.8:5.2. The mixture is continuously stirred for 10 min, and then is uniformly mixed. The mixture is sent into a process stone molding machine and is layered with reinforcing ribs, pre-installed drainage pipes and wiring pipes. The mixture is pressed into process stones, which are dried and cured at 65-75℃ for 48 h, obtaining the environment-friendly process stone resistant to water, salt erosion and weathering. After polishing and waterproof spraying treatment, the process stone is obtained. The experimental detection results are as follows:

[0102] 1, leaching toxicity detection results

[0103]

[0104] 2, mechanical property detection results

[0105]

[0106] The water absorption rate is 0.6%;

[0107] The softening coefficient is 0.85;

[0108] 3, durability detection results

[0109] Freezing resistance test: after 44 freeze-thaw cycles, there is no obvious damage and peeling;

[0110] The water permeability coefficient is 3.9*10-8 m / s;

[0111] Chloride diffusion coefficient 55*10 -14 m 2 / s;

[0112] Linear drying shrinkage 0.008%;

[0113] The test results of this batch show that the process stone has good water resistance, salt corrosion resistance and aging resistance, good volume stability, high strength, durability more than 50 years, and the toxicity leaching test and radioactive test are harmless products, reaching the requirements of environment-friendly materials, which is an environment-friendly process stone for industrial waste gypsum.

Claims

1. A method for producing an environmentally friendly process stone from industrial waste gypsum, characterized in that, It comprises the following steps: S1, solidification of soluble salt alkali water retention treatment: wet industrial waste gypsum and alkali water retention agent are placed in a mechanical mixing device, and continuously stirred for 3-60 minutes. The soluble sulfate / sulfite, phosphate, fluorophosphate adhered to the surface of the crystalline waste gypsum particles and the free soluble salt in the waste gypsum are converted into insoluble or slightly soluble calcium sulfate, calcium phosphate and calcium fluorophosphate. At the same time, the soluble heavy metal ions are converted into hydroxides which are easily combined with silicate and aluminate groups. The mixture is alkaline, and an alkaline water-retaining gypsum material is obtained. The alkali water retention agent is a substance that can react with water-soluble sulfate and fluorophosphate to form insoluble or slightly soluble minerals under aqueous conditions. S2, modification of environment-friendly process stone: under continuous stirring, the alkaline water-retaining gypsum material obtained in step S1 is added with hydraulic cementing material and heavy metal solidification hydrophobic agent in a mass ratio of 100:5-28:0.5-8. After continuous stirring for 2-30 minutes, the mixture is uniformly mixed and sent to a process stone molding machine to be pressed into process stone. The process stone is naturally cured at room temperature above 20℃ for more than 7 days, or wet heat cured at 50-98℃ for more than 24 hours, or dry steam cured at 40-98℃ for more than 24 hours, to obtain waste gypsum environment-friendly process stone with water resistance, salt corrosion resistance and weathering resistance. The heavy metal solidification hydrophobic agent is a substance that can react with zinc, lead, cadmium, mercury, manganese, copper and chromium heavy metal ions and their hydroxides in waste gypsum to form insoluble minerals and have hydrophobic characteristics. The heavy metal solidification hydrophobic agent is mainly composed of active silicate groups and / or aluminate groups and / or silicate-aluminate groups, which can solidify and coat the heavy metal ions in waste gypsum and make them hydrophobic.

2. A method of producing environment-friendly process stone from industrial waste gypsum by harmless solidification according to claim 1, characterized in that, In step S1, the substance that can react with water-soluble sulfate and fluorophosphate to form insoluble or slightly soluble minerals under aqueous conditions is at least one of high-calcium fly ash, carbide slag, lime slag powder, lime powder, calcined dolomite powder, methyl cellulose, carboxymethyl cellulose, hydroxyethyl / hydroxypropyl cellulose, sodium alginate, and superabsorbent resin.

3. A method of producing environment-friendly process stone from industrial waste gypsum by harmless solidification according to claim 1 or 2, characterized in that, In step S1, the amount of the alkali water retention agent is 1.0%-19.8% of the mass of the wet industrial waste gypsum. The specific amount is selected according to the content of soluble salts such as sulfate and fluorophosphate and the water content in the wet industrial waste gypsum. When the content of soluble salts in the wet industrial waste gypsum is high and the water content is high, the upper value is selected.

4. The method of claim 1 or 2, wherein the method is characterized by, In step S1, the wet industrial waste gypsum is fresh phosphogypsum or desulfurization gypsum in wet state, with a water content of 6%-32%; or phosphogypsum or desulfurization gypsum with a water content of <32% stored in a slag pool or slag storage, or phosphogypsum or desulfurization gypsum that has been dried, crushed and wetted with an appropriate amount of water.

5. A method of producing environment-friendly process stone from industrial waste gypsum by harmless solidification according to claim 3, characterized in that, In step S1, the wet industrial waste gypsum is fresh phosphogypsum or desulfurization gypsum in wet state, with a water content of 6%-32%; or phosphogypsum or desulfurization gypsum with a water content of <32% stored in a slag pool or slag storage, or phosphogypsum or desulfurization gypsum that has been dried, crushed and wetted with an appropriate amount of water.

6. The method of claim 1 or 2, wherein the method is characterized by, In step S1, the alkalinity is pH≥12.

7. A method of producing environment-friendly process stone from industrial waste gypsum by harmless solidification according to claim 3, characterized in that, In step S1, the alkaline is at a pH value ≥ 12.

8. A method of producing environment-friendly process stone from industrial waste gypsum by harmless solidification according to claim 4, characterized in that, In step S1, the alkaline is at a pH value ≥ 12.

9. A method of producing environment-friendly process stone from industrial waste gypsum by harmless solidification according to claim 1 or 2, characterized in that, In step S2, the hydraulic cementitious material is at least one of Portland cement, aluminate cement, sulfoaluminate cement, double-quick cement, and slag fly ash type active slag powder.

10. A method of manufacturing environment-friendly process stone from industrial waste gypsum by solidification and detoxification, according to claim 3, characterized in that, In step S2, the hydraulic cementitious material is at least one of Portland cement, aluminate cement, sulfoaluminate cement, double-quick cement, and slag fly ash type active slag powder.

11. A method of producing environment-friendly process stone from industrial waste gypsum by harmless solidification according to claim 4, characterized in that, In step S2, the hydraulic cementitious material is at least one of Portland cement, aluminate cement, sulfoaluminate cement, double-quick cement, and slag fly ash type active slag powder.

12. A method of manufacturing environment-friendly process stone from industrial waste gypsum by solidification and detoxification, as claimed in claim 6, wherein, In step S2, the hydraulic cementitious material is at least one of Portland cement, aluminate cement, sulfoaluminate cement, double-quick cement, and slag fly ash type active slag powder.

13. A method of manufacturing environment-friendly process stone from industrial waste gypsum by harmless solidification according to claim 1 or 2, characterized in that, In step S2, the hydraulic cementitious material is at least one of Portland cement, aluminate cement, sulfoaluminate cement, double-quick cement, and slag fly ash type active slag powder.

14. A method of manufacturing environment-friendly process stone from industrial waste gypsum by solidification and detoxification, according to claim 3, characterized in that, In step S2, during the stirring, semi-hydrated or anhydrous gypsum powder, or building sand and gravel aggregates, or waste concrete granular materials, or tailings sand, or other industrial waste residues that do not produce antagonistic destructive effects are added.

15. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 4, characterized in that, In step S2, during the stirring, semi-hydrated or anhydrous gypsum powder, or building sand and gravel aggregates, or waste concrete granular materials, or tailings sand, or other industrial waste residues that do not produce antagonistic destructive effects are added.

16. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 6, characterized in that, In step S2, during the stirring, semi-hydrated or anhydrous gypsum powder, or building sand and gravel aggregates, or waste concrete granular materials, or tailings sand, or other industrial waste residues that do not produce antagonistic destructive effects are added.

17. A method of manufacturing environment-friendly process stone from industrial waste gypsum, according to claim 9, characterized in that, In step S2, during the stirring, semi-hydrated or anhydrous gypsum powder, or building sand and gravel aggregates, or waste concrete granular materials, or tailings sand, or other industrial waste residues that do not produce antagonistic destructive effects are added.

18. A method of manufacturing environment-friendly process stone from industrial waste gypsum by solidification and detoxification, according to claim 1 or 2, characterized in that, In step S2, during the stirring, semi-hydrated or anhydrous gypsum powder, or building sand and gravel aggregates, or waste concrete granular materials, or tailings sand, or other industrial waste residues that do not produce antagonistic destructive effects are added.

19. A method of manufacturing environment-friendly process stone from industrial waste gypsum, according to claim 3, characterized in that, In step S2, during the stirring, semi-hydrated or anhydrous gypsum powder, or building sand and gravel aggregates, or waste concrete granular materials, or tailings sand, or other industrial waste residues that do not produce antagonistic destructive effects are added.

20. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 4, characterized in that, In step S2, during the molding, reinforcing bars or nets are laid, and / or drainage or wiring pipes are pre-installed.

21. A method of manufacturing environment-friendly process stone from industrial waste gypsum by solidification and detoxification, as claimed in claim 6, wherein, In step S2, during the molding, reinforcing bars or nets are laid, and / or drainage or wiring pipes are pre-installed.

22. A method of manufacturing environment-friendly process stone from industrial waste gypsum, according to claim 9, characterized in that, In step S2, during the molding, reinforcing bars or nets are laid, and / or drainage or wiring pipes are pre-installed.

23. A method of manufacturing environment-friendly process stone from industrial waste gypsum, according to claim 13, characterized in that, In step S2, during the molding, reinforcing bars or nets are laid, and / or drainage or wiring pipes are pre-installed.

24. A method of manufacturing environment-friendly process stone from industrial waste gypsum, according to claim 1 or 2, characterized in that, In step S2, during the molding, reinforcing bars or nets are laid, and / or drainage or wiring pipes are pre-installed.

25. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 3, characterized in that, In step S2, during the molding, reinforcing bars or nets are laid, and / or drainage or wiring pipes are pre-installed.

26. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 4, characterized in that, In step S2, the environmentally friendly process stone prepared is further subjected to impregnation and / or spray waterproofing treatment.

27. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 6, characterized in that, In step S2, the environmentally friendly process stone prepared is further subjected to impregnation and / or spray waterproofing treatment.

28. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 9, characterized in that, In step S2, the environmentally friendly process stone prepared is further subjected to impregnation and / or spray waterproofing treatment. In step S2, the environmentally friendly process stone prepared is further subjected to impregnation and / or spray waterproofing treatment. In step S2, the environmentally friendly process stone prepared is further subjected to impregnation and / or spray waterproofing treatment. In step S2, the environmentally friendly process stone prepared is further subjected to impregnation and / or spray waterproofing treatment.

29. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 13, characterized in that, In step S2, the environment-friendly process stone prepared is further subjected to waterproofing treatment by dipping and / or spraying.

30. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 18, characterized in that, In step S2, the environment-friendly process stone prepared is further subjected to waterproofing treatment by dipping and / or spraying.

31. A method of manufacturing environment-friendly process stone from industrial waste gypsum, according to claim 1 or 2, characterized in that, In step S2, the environment-friendly process stone prepared is further subjected to decorative spraying and / or polishing.

32. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 3, characterized in that, In step S2, the environment-friendly process stone prepared is further subjected to decorative spraying and / or polishing.

33. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 4, characterized in that, In step S2, the environment-friendly process stone prepared is further subjected to decorative spraying and / or polishing.

34. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 6, characterized in that, In step S2, the environment-friendly process stone prepared is further subjected to decorative spraying and / or polishing.

35. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 9, characterized in that, In step S2, the environment-friendly process stone prepared is further subjected to decorative spraying and / or polishing.

36. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 13, characterized in that, In step S2, the environment-friendly process stone prepared is further subjected to decorative spraying and / or polishing.

37. A method of manufacturing environment friendly process stone from industrial waste gypsum decontaminated and solidified according to claim 18, characterized in that, In step S2, the environment-friendly process stone prepared is further subjected to decorative spraying and / or polishing.

38. A method of manufacturing environment-friendly process stone from industrial waste gypsum, according to claim 24, characterized in that, In step S2, the environment-friendly process stone prepared is further subjected to decorative spraying and / or polishing.

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