CN110204237B - Production method of cement retarder - Google Patents
Production method of cement retarder Download PDFInfo
- Publication number
- CN110204237B CN110204237B CN201910576555.3A CN201910576555A CN110204237B CN 110204237 B CN110204237 B CN 110204237B CN 201910576555 A CN201910576555 A CN 201910576555A CN 110204237 B CN110204237 B CN 110204237B
- Authority
- CN
- China
- Prior art keywords
- gypsum
- cement retarder
- semi
- cement
- hydrated gypsum
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/46—Sulfates
- C01F11/466—Conversion of one form of calcium sulfate to another
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B22/00—Use of inorganic materials as active ingredients for mortars, concrete or artificial stone, e.g. accelerators, shrinkage compensating agents
- C04B22/08—Acids or salts thereof
- C04B22/14—Acids or salts thereof containing sulfur in the anion, e.g. sulfides
- C04B22/142—Sulfates
- C04B22/143—Calcium-sulfate
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/20—Retarders
- C04B2103/22—Set retarders
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention discloses a production method of a cement retarder, belonging to the field of comprehensive utilization of gypsum. The invention solves the technical problems that the existing preparation process of the gypsum cement retarder has long aging time and unstable setting time when added into cement. The production method of the cement retarder comprises the following steps: mixing water, sulfuric acid and phosphoric acid to obtain a liquid-phase medium, adding the semi-hydrated gypsum into the liquid-phase medium to obtain mixed slurry, carrying out recrystallization reaction under the heating condition to fully convert the semi-hydrated gypsum into dihydrate gypsum, and then filtering and washing to obtain the cement retarder. The cement retarder prepared by the invention meets the GB/T23456-2018 phosphogypsum primary standard, and the initial and final setting time meets the GB/T21371-2008 quality standard of industrial byproduct gypsum used in cement. The method has the advantages of short flow, low energy consumption and stable quality index, and can recover water-soluble phosphorus and eutectic phosphorus in the gypsum and realize the cyclic utilization of resources.
Description
Technical Field
The invention belongs to the field of comprehensive utilization of gypsum, and particularly relates to a production method of a cement retarder.
Background
The cement retarder is an additive which can delay cement hydration reaction, thereby prolonging the setting time of concrete, keeping the plasticity of fresh concrete for a long time, facilitating the pouring, improving the construction efficiency and simultaneously not causing adverse effect on various performances of the later stage of the concrete. The retarder for applying gypsum to cement has been introduced in the prior art, and mainly comprises natural gypsum and industrial by-product gypsum (desulfurized gypsum, dihydrate phosphogypsum, hemihydrate phosphogypsum, titanium gypsum, citric acid gypsum and the like). The natural gypsum and the desulfurized gypsum can be directly used as cement retarders, but the natural gypsum is mined by the national restriction, the productivity cannot meet the requirements of the cement industry, the desulfurized gypsum cannot meet the demand of the retarders, and the cost of the desulfurized gypsum is high.
With the rapid development of phosphate fertilizer industry in China, the amount of byproduct phosphogypsum is increased sharply, the annual emission amount of the phosphogypsum reaches about 5000 kilotons, the technical bottleneck exists in resource utilization, the phosphogypsum digestion amount is small, and the accumulated stockpiling amount exceeds 2 hundred million tons. Among them, phosphogypsum hemihydrate is an industrial waste residue discharged in the process of producing wet-process phosphoric acid, and generally contains more calcium sulfate hemihydrate (CaSO)4·1/2H2O) contains a small amount of impurities such as incompletely decomposed phosphate ore, fluoride, phosphoric acid, organic matter, acid-insoluble substances, iron-aluminum compounds, etc. Most phosphogypsum is stockpiled and treated, which not only occupies land, but also wastes resources, and the contained acid and other harmful substances easily cause pollution to the surrounding environment. Therefore, the ardealite reaches the place that the ardealite cannot be treated vigorously, otherwise, harmony of people, environment and society and homeland protection are directly influenced, unexpected loss is directly brought to survival and development of enterprises, and the development and application of the ardealite become urgent.
Chinese patent CN101792278A discloses a method for producing cement retarder by using phosphogypsum, which uses dihydrate phosphogypsum to mix with carbide slag, and the time of granulation and aging is more than 24 hours. Patent CN1887773A discloses a cement retarder and a production method thereof, wherein dihydrate phosphogypsum, semi-hydrated phosphate paste and water are mixed according to a certain proportion, stirred, pelletized, coagulated and hardened to obtain a product, but the process can not solidify water-soluble phosphorus in gypsum, and the coagulation time can be influenced. Patents CN104072003A and CN108996937A also mention the method of preparing cement retarder from industrial by-product gypsum. The prior art mostly adopts dry mixing of phosphogypsum, or mixing and aging of byproduct gypsum and alkaline substances, belongs to solid-liquid reaction in the chemical field, has insufficient reaction and long aging time, and has unstable setting time when being added into cement as a retarder, so that the retarder can not be well popularized and accepted in the cement industry.
Disclosure of Invention
The invention aims to solve the technical problems that the existing preparation process of the gypsum cement retarder has long aging time and unstable setting time when added into cement.
The technical scheme for solving the problems is to provide a production method of the cement retarder, which comprises the following steps: mixing water, sulfuric acid and phosphoric acid to obtain a liquid-phase medium with a certain concentration, adding the semi-hydrated gypsum into the liquid-phase medium to obtain a mixed slurry, carrying out recrystallization reaction at a certain temperature to fully convert the semi-hydrated gypsum into dihydrate gypsum, and then filtering, separating and washing to obtain the cement retarder.
Wherein P is in a liquid medium2O5Mass concentration<30％，SO3Mass concentration<10％。
Wherein the recrystallization reaction temperature is 40-95 ℃.
Wherein the recrystallization time is controlled to be more than or equal to 0.5 h.
Wherein, the content of gypsum crystal water is controlled to be more than or equal to 19 percent after the reaction is finished.
Wherein, the filtration separation comprises filtration and filter-pressing separation equipment.
Wherein, the water content of the cement retarder is controlled to be less than 20 percent.
Wherein the semi-hydrated gypsum comprises natural semi-hydrated gypsum and industrial by-product semi-hydrated gypsum.
Wherein, part of the filtrate obtained by filtering and separating and the washing water after washing are returned to the liquid phase medium for recycling after adjusting the liquid phase index.
The invention has the beneficial effects that:
the invention adopts semi-hydrated gypsum as a raw material, controls a certain liquid phase condition, fully converts the semi-hydrated gypsum into dihydrate gypsum through recrystallization, and obtains the water-soluble P of the cement retarder2O5Content (wt.)<0.35% and water-soluble F content<0.3 percent and eutectic phosphorus less than 0.35 percent, and meets the quality standard requirement of GB/T21371-2008 on industrial by-product gypsum in cement; the recrystallization process of the invention completes CaSO4·1/2H2O→CaSO4·2H2Conversion of O, advantageouslyThe impurities in the semi-hydrated gypsum are dissolved, so that the purity of the cement retarder is improved, particularly, for byproduct phosphogypsum, intercrystalline impurities can be effectively released through recrystallization, and eutectic phosphorus, water-soluble phosphorus, fluorine and organic matters are effectively reduced; compared with the lime neutralization process, the cement retarder prepared by the recrystallization method has high purity and stable quality, can effectively eliminate the influence of incomplete neutralization of the eutectic phosphorus on the stability of the quality index of the retarder, and can recover the phosphorus pentoxide in the phosphogypsum; the method for preparing the cement retarder by using the semi-hydrated gypsum as the raw material has the advantages of short flow, low energy consumption, stable quality index, realization of resource recycling and suitability for popularization and application in the field.
Drawings
FIG. 1 is a schematic process flow diagram of one embodiment of the present invention.
Detailed Description
We have found phosphogypsum hemihydrate (CaSO)4·1/2H2O) has no function of delaying the setting time of cement in the cement retarder, and the substance for delaying the setting time in the cement retarder is dihydrate gypsum (CaSO)4·2H2O), the additive amount of dihydrate gypsum in cement is 3% -5%, sulfate radical in the retarder reacts with calcium aluminate in the cement, and the material of production wraps up in the cement granule surface to a certain extent prevents the cement hydration, thereby prolongs the setting time of concrete, makes newly-mixed concrete keep plasticity for a long time, and the convenient pouring improves the efficiency of construction, can not cause harmful effects to concrete later stage each item performance simultaneously.
Based on the research, in order to solve the problems of long aging time and unstable setting time when the existing gypsum cement retarder is added into cement in the preparation process, the invention provides a method for preparing a cement retarder by a semi-hydrated gypsum recrystallization method, which comprises the following steps: mixing water, sulfuric acid and phosphoric acid to obtain a liquid-phase medium, adding the semi-hydrated gypsum into the liquid-phase medium to obtain a mixed slurry, carrying out recrystallization reaction under a heating condition to fully convert the semi-hydrated gypsum into dihydrate gypsum, and then filtering, separating and washing to obtain the cement retarder. The method can be specifically carried out according to the following operations:
a. adding sulfuric acid and phosphoric acid into water to prepare a semi-hydrated gypsum recrystallization liquid phase medium;
b. heating the liquid phase medium to meet the condition of preparing the cement retarder by recrystallizing the semi-hydrated gypsum;
c. b, adding the semi-hydrated gypsum into the liquid phase medium obtained in the step b, and keeping the temperature for a certain retention time to fully convert the semi-hydrated gypsum into dihydrate gypsum;
d. c, filtering and separating the mixed slurry obtained in the step c to obtain filtrate and filter cakes;
e. and washing the filter cake with clear water to obtain the cement retarder and washing water.
Wherein P is in a liquid medium2O5Mass concentration<30％，SO3Mass concentration<10％。
Wherein the heating temperature is 40-95 ℃.
Wherein the recrystallization time is controlled to be more than or equal to 0.5 h.
Wherein, the content of gypsum crystal water is controlled to be more than or equal to 19 percent after the reaction is finished. Specifically, the crystal form can be observed through a microscope, and the crystal water is sampled and determined according to the product sampling standard.
Wherein, the filtration separation comprises filtration and filter-pressing separation equipment.
Wherein, the water content of the cement retarder is controlled to be less than 20 percent.
And c, adjusting liquid phase indexes of part of filtrate obtained in the step d and washing water obtained in the step e, and returning the part of filtrate to the liquid phase medium for recycling.
The raw material of the semi-hydrated gypsum adopted by the invention can be any semi-hydrated gypsum, mainly comprising natural semi-hydrated gypsum and industrial by-product semi-hydrated gypsum.
Preferably, the hemihydrate gypsum of the invention has a purity of more than 90% and a particle size of 100% passing through a 100-mesh standard sieve.
In order to better control the moisture content of the cement retarder, a drying step can be adopted after the cement retarder is washed by clear water, and finally a cement retarder product is obtained.
The invention is further illustrated and described by the following examples.
Example 1
a. Adding sulfuric acid and phosphoric acid into water to prepare a semi-hydrated gypsum recrystallization liquid phase medium, liquid phase P2O5Liquid phase SO with concentration of 25%3The concentration is 8%;
b. heating the liquid phase medium in the step a to 45 ℃ to meet the condition of preparing the retarder by the recrystallization of the semi-hydrated gypsum;
c. b, adding the semi-hydrated gypsum into the liquid phase medium in the step b, and standing for 30min to fully convert the semi-hydrated gypsum into dihydrate gypsum;
d. c, filtering and separating the slurry obtained in the step c to obtain a filter cake and a filtrate;
e. washing the filter cake in the step d with clean water to obtain a cement retarder;
f. and (c) returning part of filtrate in the step d and all washing water in the step e to the step b.
Example 2
a. Adding sulfuric acid and phosphoric acid into water to prepare a semi-hydrated gypsum recrystallization liquid phase medium, liquid phase P2O5Liquid phase SO with concentration of 20%3The concentration is 4%;
b. heating the liquid phase medium in the step a to 60 ℃ to meet the condition of preparing the retarder by recrystallizing the semi-hydrated gypsum;
c. b, adding the semi-hydrated gypsum into the liquid phase medium in the step b, and allowing the semi-hydrated gypsum to be fully converted into dihydrate gypsum after the residence time of 60 min;
d. filtering and separating the slurry obtained in the step c to obtain a filter cake and a filtrate;
e. washing the filter cake in the step d with clean water to obtain a cement retarder;
f. and (c) returning part of filtrate in the step d and all washing water in the step e to the step b.
Example 3
a. Adding sulfuric acid and phosphoric acid into water to prepare a semi-hydrated gypsum recrystallization liquid phase medium, liquid phase P2O5Liquid phase SO with concentration of 10%3The concentration is 2%;
b. heating the liquid phase medium in the step a to 75 ℃ to meet the condition of preparing the retarder by the recrystallization of the semi-hydrated gypsum;
c. b, adding the semi-hydrated gypsum into the liquid phase medium in the step b, and allowing the semi-hydrated gypsum to be fully converted into dihydrate gypsum after the residence time of 90 min;
d. filtering and separating the slurry obtained in the step c to obtain a filter cake and a filtrate;
e. washing the filter cake in the step d with clean water to obtain a cement retarder;
f. and (c) returning part of filtrate in the step d and all washing water in the step e to the step b.
Example 4
a. Adding sulfuric acid and phosphoric acid into water to prepare a semi-hydrated gypsum recrystallization liquid phase medium, liquid phase P2O5Liquid phase SO with concentration of 5%3The concentration is 1%;
b. heating the liquid phase medium in the step a to 85 ℃ to meet the condition of preparing the retarder by recrystallizing the semi-hydrated gypsum;
c. b, adding the semi-hydrated gypsum into the liquid phase medium in the step b, and standing for 120min to fully convert the semi-hydrated gypsum into dihydrate gypsum;
d. filtering and separating the slurry obtained in the step c to obtain a filter cake and a filtrate;
e. washing the filter cake in the step d with clean water to obtain a cement retarder;
f. and (c) returning part of filtrate in the step d and all washing water in the step e to the step b.
Comparative example 1 Natural Gypsum
Comparative example 2 desulfurized Gypsum
Comparative example 3 aged Gypsum
Comparative example 4 hemihydrate Gypsum + 5% lime
The gypsum of examples 1-4 and comparative examples 1-4 is tested as the setting performance of the cement retarder by referring to the quality standard GB/T21371-2008 for the industrial byproduct gypsum in the cement, the initial setting time, the final setting time and the compressive strength are respectively counted, and the statistical results are shown in Table 1.
TABLE 1 initial setting time, final setting time and compressive strength
In the above embodiment, hemihydrate gypsum is used as raw material, certain concentrations of phosphoric acid and sulfuric acid are controlled, and the liquid phase conversion temperature and time are adjusted under the condition of satisfying recrystallization conditionsComplete CaSO4·1/2H2O→CaSO4·2H2And the crystal transformation of O to obtain the gypsum which meets the quality standard of GB/T21371-2008 for industrial by-product gypsum in cement. As can be seen from Table 1, the cement retarder prepared by the method of the invention has better performance than aged gypsum and lime neutralized modified gypsum, each performance can be comparable to desulfurized gypsum and natural gypsum, and the cement retarder has better economic value and market prospect.
Claims (7)
1. The production method of the cement retarder is characterized by comprising the following steps: mixing water, sulfuric acid and phosphoric acid to obtain a liquid-phase medium with a certain concentration, adding the semi-hydrated gypsum into the liquid-phase medium to obtain a mixed slurry, carrying out recrystallization reaction at a certain temperature to fully convert the semi-hydrated gypsum into dihydrate gypsum, and then filtering, separating and washing to obtain a cement retarder;
p in the liquid medium2O5Mass concentration<30%，SO3Mass concentration<10%；
The recrystallization reaction temperature is 40-95 ℃;
the recrystallization reaction time is controlled to be more than or equal to 0.5 h.
2. The method for producing a cement retarder according to claim 1, characterized in that: after the reaction is finished, the content of the gypsum crystal water is controlled to be more than or equal to 19 percent.
3. The method for producing a cement retarder according to claim 1, characterized in that: the filtration separation equipment comprises filtration and pressure filtration separation equipment.
4. The method for producing a cement retarder according to claim 1, characterized in that: controlling the water content of the cement retarder to be less than 20%.
5. The method for producing a cement retarder according to claim 1, characterized in that: the semi-hydrated gypsum comprises natural semi-hydrated gypsum and industrial by-product semi-hydrated gypsum.
6. The method for producing a cement retarder according to claim 1 or 5, characterized in that: the semi-hydrated gypsum has the purity of more than 90 percent and the particle size of 100 percent passing through a 100-mesh standard sieve.
7. The method for producing a cement retarder according to claim 1, characterized in that: part of filtrate obtained by filtering and separating and washing water after washing are returned to the liquid phase medium for recycling after adjusting liquid phase indexes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910576555.3A CN110204237B (en) | 2019-06-28 | 2019-06-28 | Production method of cement retarder |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910576555.3A CN110204237B (en) | 2019-06-28 | 2019-06-28 | Production method of cement retarder |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN110204237A CN110204237A (en) | 2019-09-06 |
| CN110204237B true CN110204237B (en) | 2022-04-05 |
Family
ID=67795380
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910576555.3A Active CN110204237B (en) | 2019-06-28 | 2019-06-28 | Production method of cement retarder |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN110204237B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111484265B (en) * | 2020-04-22 | 2022-02-18 | 四川清固新材料有限公司 | Cement retarder prepared from nickel gypsum waste residues and preparation method thereof |
| CN111732361B (en) * | 2020-04-24 | 2022-01-25 | 四川省星船城水泥股份有限公司 | Production method for using multisource industrial by-product gypsum as cement retarder |
| CN116040970B (en) * | 2022-09-08 | 2023-08-18 | 河南建筑材料研究设计院有限责任公司 | Eutectic phosphorus removal system of phosphogypsum |
| CN116535149A (en) * | 2023-05-08 | 2023-08-04 | 西部(重庆)地质科技创新研究院有限公司 | Cementing stabilizing material for controlling release of heavy metal in tailing pond and preparation method thereof |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| UA36267U (en) * | 2008-03-17 | 2008-10-27 | Национальный Университет Водного Хозяйства И Природопользования | Dry plaster mixture for finishing work |
| CN102001636A (en) * | 2010-09-26 | 2011-04-06 | 四川大学 | Method for producing broad-concentration phosphoric acid and clean plaster by middle-low grade phosphorus ore wet process |
| CN106866015A (en) * | 2017-03-15 | 2017-06-20 | 河北科技大学 | A kind of β semi-hydrated gypsums retarder and preparation method thereof |
| CN109734344A (en) * | 2019-03-05 | 2019-05-10 | 昆明川金诺化工股份有限公司 | A method of cement retarder is prepared using half water ardealite |
-
2019
- 2019-06-28 CN CN201910576555.3A patent/CN110204237B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| UA36267U (en) * | 2008-03-17 | 2008-10-27 | Национальный Университет Водного Хозяйства И Природопользования | Dry plaster mixture for finishing work |
| CN102001636A (en) * | 2010-09-26 | 2011-04-06 | 四川大学 | Method for producing broad-concentration phosphoric acid and clean plaster by middle-low grade phosphorus ore wet process |
| CN106866015A (en) * | 2017-03-15 | 2017-06-20 | 河北科技大学 | A kind of β semi-hydrated gypsums retarder and preparation method thereof |
| CN109734344A (en) * | 2019-03-05 | 2019-05-10 | 昆明川金诺化工股份有限公司 | A method of cement retarder is prepared using half water ardealite |
Also Published As
| Publication number | Publication date |
|---|---|
| CN110204237A (en) | 2019-09-06 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110204237B (en) | Production method of cement retarder | |
| EP3351506B1 (en) | Method for producing phosphoric acid and by-producing alpha-hemihydrate gypsum by wet-process | |
| RU2690358C1 (en) | Method for production of extraction phosphoric acid with obtained as by-product of alpha-hemihydrate gypsum and alpha-semi-aqueous gypsum with high degree of purity and high degree of whiteness | |
| CN109734344B (en) | Method for preparing cement retarder by using semi-hydrated phosphogypsum | |
| CN109734105B (en) | Method for self-enrichment and whole-quantity utilization of titanium gypsum by cyclic conversion of metal | |
| CN109179476B (en) | Method for controlling water content of titanium gypsum | |
| CN104176963A (en) | Phosphorus gypsum cement retarder | |
| CN111825408A (en) | Sludge curing agent prepared from steel slag modified phosphogypsum and use method thereof | |
| CN111994938B (en) | Method for preparing calcium sulfate whisker from calcium carbide slag modified phosphogypsum | |
| CN110194605A (en) | A method of building gypsum is prepared using ardealite | |
| CN110372233A (en) | Sulphoaluminate cement clinker and cement of a kind of titanium gypsum resource utilization and preparation method thereof | |
| CN113120875A (en) | Production method of low-impurity wet-process phosphoric acid and high-quality alpha-hemihydrate gypsum | |
| CN104310830A (en) | Method for producing beta-high-purity gypsum powder by using phosphogypsum | |
| CN103232052B (en) | Method for preparing high-purity calcium carbonate directly from phosphogypsum | |
| CN113185178B (en) | Phosphogypsum cement retarder and preparation method thereof | |
| CN112591782B (en) | Conversion and purification method of low-consumption dihydrate phosphogypsum | |
| CN108439451A (en) | The method for preparing precipitated calcium carbonate using ardealite | |
| CN1226222C (en) | Method for producing building gypsum powder using phosphrus gypsum | |
| CN115925297B (en) | Calcination purification method for acid phosphogypsum | |
| CN111847956A (en) | Phosphogypsum-based cement retarder and preparation method and application thereof | |
| CN108314342B (en) | Method for preparing alpha-type high-strength gypsum from dihydrate phosphogypsum | |
| CN112250051B (en) | Method for co-producing phosphoric acid and cement clinker by absorbing phosphogypsum roasting smoke by phosphorite slurry | |
| CN115057639A (en) | Method for preparing alpha semi-hydrated gypsum from fluorgypsum | |
| CN114804673A (en) | Comprehensive utilization method of red mud | |
| CN115925301A (en) | Concrete waste slurry treatment process and concrete preparation method thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |