How Gypsum is Processed | M&C - Mining & Construction

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Definition of Gypsum

Gypsum ( CaSO4·2H2O) is a natural monoclinic minera, Its main chemical component is calcium sulfate hydrate, which is widely distributed in the salt lake sediments formed by evaporation and widely used as industrial materials and building materials.

History of Gypsum

The English word for plaster is &#;Gypsum&#;, and German is &#;Gyps&#;. It all comes from the Greek γύψος (gypsos), and then the Latin word is &#;gypsus&#;. At that time, it didn&#;t mean gypsumin the modern sense, but meant something like moonstone.

Gypsum was used as a building material in the Neolithic Age and was used for interior decoration in Anatolia (now in Turkey) in BC. Evidence of the use of plaster was later found in Sumir and Babylon sites, such as Jericho in BC (now in Israel) and Uluk in BC (now in Iraq). The Pyramid of Khufu and the Sphinx, built in BC, used gypsum mortar as a cementitious material to bond and masonry stones.

Properties of Gypsum

Gypsum is a very common soft sulfate mineral, which can be easily identified by its hardness, cleavage and solubility in water:

PropertiesValuePropertiesValueNameGypsumMelting&#;&#;FormulaCaSO4·2H2OSolubilitysoluble in waterMolecular172CleavagePerfectColourWhite, colorless, or yellow-redHardness2 mohsLustreVitreous, Silky, PearlyTenacityFlexibleTransparencyTransparent, Translucent, OpaqueDensity2.31&#;2.33 g/cm3StreakWhiteCrystal StatePlate, fibrous, bulk or fine grainedCrystalMonoclinicApplicationArchitectural, Medical

Classification of Gypsum

Gypsum usually refers to two kinds of minerals: raw gypsum and anhydrite.

Raw Gypsum is calcium sulfate dihydrate ((Ca (SO4) 2H2O), also known as gypsum dihydrate, gypsum or gypsum, composition CaO (32.6%), SO3 (46.5%), H2O+ (20.9%), monoclinic system, crystal is plate-like, usually dense block or fiber, white or gray, red, brown, vitreous or silky luster, Mohs hardness is 2, density 2.3g/cm3.

Anhydrite is anhydrous calcium sulfate (Ca (SO4)), theoretical component CaO (41.2%), SSO3 (58.8%), orthorhombic system, crystal is plate, usually dense block or granular, white, grayish white, vitreous luster, Morse hardness is 3 &#; 3.5, density 2.8~3.0g/cm3.

Raw gypsum and anhydrite are often produced together, and anhydrite can be formed by calcining gypsum at 400 &#; 500 °C.

How is Gypsum Formed

Gypsum is a widely distributed mineral, which is mainly formed by sedimentation and weathering, and a few are found in hydrothermal sulphide deposits. Gypsum usually can be fond in the form of crystals or deposits beds.

Gypsum formed in sea basins and lake basins is formed by evaporation of brine or hydration of anhydrite; symbiosis with anhydrite, gypsum, etc. It is layered or lenticular in the interlayer of limestone, red shale, marl and sandy clay. The gypsum in the oxidation zone of sulphide deposits is mainly caused by sulfides.

Distribution of Gypsum

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The world&#;s largest producer of gypsum is the United States. In the United States, gypsum deposits are distributed in 22 states with a total of 69 mines, with the largest producing area in Fort Dodge, Iowa, followed by Canada. France takes the lead in European gypsum production, followed by Germany, the United Kingdom and Spain.

Use of Gypsum

Gypsum is a widely used industrial material and building material. Gypsum (CaSO4 ·2H2O) can be calcined and grinded to obtain β-type hemihydrate gypsum (2CaSO4 ·H2O), that is, building gypsum, also known as cooked gypsum or plaster. The model gypsum can be obtained when the calcination temperature is 190 °C, and its fineness and whiteness are higher than that of building gypsum. If raw gypsum is calcined at 400 °C or above 800 °C, floor gypsum can be obtained, its setting and hardening are slow, but the strength, wear resistance and water resistance of hardened gypsum are better than that of ordinary building gypsum.

1. Building Gypsum: Mostly used in building mold ash, painting, masonry mortar and all kinds of gypsum products.
2. Model Gypsum: less impurities, white color, mainly used for ceramic culture process, a small amount for decorative relief.
3. Floor Gypsum: Mainly used for demanding mold ash engineering, decorative products and plasterboard.
4. Whitewash Gypsum: Made of cementing material with appropriate amount of retarder, water-retaining agent and other chemical admixtures.

In addition, gypsum can also be used in the manufacture of cement, sulfuric acid, soil improvers, food coagulants, pesticide diluents as well as medical and cosmetology.

How is Gypsum Processed

The raw material of gypsum powder is natural gypsum ore, and the production process of gypsum powder is mainly divided into 5 stages: crushing, screening, grinding, calcination, storage and transportation.

1. Crushing: The mined gypsum ore raw material enters the crusher through vibrating feeder, and the crusher break the large-size gypsum ore into small particles smaller than 30mm, and then waits for further screening treatment.
2. Screening: Use a vibrating screen to separate incomplete large particles and impurities that mixed in crushed gypsum. Gypsum with suitable available size can be separated by controlling the diameter of sieve hole, which can be used as cement additive for sale. Or go straight to the next stage.
3. Grinding: The screened gypsums are fed into the grinding mill uniformly and continuously by vibratory feeders for grinding. The ground gypsum powder is blown out by the air flow bulged by the mill blower and graded by the separator machine on the mill. The fineness qualified powder is collected by hydrocyclone and discharged through the powder outlet tube, is know as land plaster. Land plaster is sent by screw conveyor. As a soil conditioner, or transported to calcination.
4. Calcination: Calcination mainly uses the direct contact between high-temperature hot flue gas of boiling furnace and gypsum raw materials to complete the calcination and dehydration of gypsum powder. The structure and characteristics of dehydrated gypsum are also different under different heating conditions.
5. Storage Transportation: The calcined qualified gypsum powder is sent to the clinker warehouse for storage or into the workshop to produce gypsum board, cement and other gypsum products.

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gypsum powder making machine line

phospho gypsum powder production line/china factory naturalgypsum powder production line

Raw material request

Main quality indexes of raw materials CaSO4·2H2O content: 75% ~ 95% Surface water content  &#; 18% Crystal water content  18-20% Capacity 15,000ton-400,000ton/year , based on 24hour/day ,300days/year  Fuel  Gas /coal /heavy oil/diesel Electricity  380V/50HZ  Quality standard Quality meets and exceeds the national standard of gypsum powder Construction gypsum national standard number GB -88
 

Powder parameters

1.Product quality Reach or exceed the china (GB-88building gypsum) requirements. 2.Fineness 100 mesh-120mesh 3.Bending strength  Bending strength 1.8 Mpa; Compressive strength: was 3.0 Mpa.(The bending strength have direct relations with raw material)  4.Main relative composition 1)Soluble anhydrous gypsum content:&#; 80% adjustable 2)The content of dihydrate gypsum: < 5% adjustable 3)Initial setting time: 3 ~ 8 min adjustable; Final setting time: 6 ~ 15 min adjustable. 4)Scale thick: 78 ~ 85% adjustable.

Labor requirements

From raw materials to drying  1 person /8 hours Heating supply  1 person /8 hours Calcinate control     1 person /8 hours Electrical work     1 person /12 hours Machine repair   1 person /12 hours

Unique advantage

 

1.Hammer dryer

Function :The air dryer is used to bake the gypsum powder water containing less than 5% before entering the boiling furnace.
this step can increase the gypsum liquidity .when it come to the boiling furnace ,it can easy to calcinate ,so we have this step 

 
 

2.Modification grinding(ball mill )

Function :Because the chemical gypsum powder has the quality problem, through the modification grinding, changes the chemical gypsum component characteristic, make the quality similar to the natural gypsum powder.

 

3.FD - chamber boiling furnace technology(hot iar )

The technology of FD - chamber boiling furnace technology can effectively prevent the mixing of raw materials with gypsum powder in the process of calcining .Traditional calcining technologies such as vertical boiling furnace , rotary kiln ,general boiling furnace, etc.Due to the effect of mixing function of the machinery and air flow, dihydrate gypsum ,semi-hydratedgypsum and anhydrite gypsum three-phase blending mutually in the process of boiling dehydration,It is inevitable that the phase composition of the final product will be polyphasic, and the product quality index will be reduced significantly.And FD - chamber fluid bed calcining process changes according to the temperature curve of gypsum powder , artificially divide calcining process into four relatively independent dehydration space, effectively avoid the phenomenon of high and low temperature material blending and the composition of the final product was improved .In the 1 and 2 areas of the main calcining furnace, high temperature heat transfer technology is adopted to rapidly heat and dehydrate the materials that have just entered the FD- chamber boiling furnace, and slowly dehydrate in the 3 and 4 areas.Under the action of high pressure wind, the whole material presents a fluid boiling state, which improves the efficiency of heat transfer and mass transfer in gas and solid powder..
 

 

 Hot air boiling furnace and hot oil furnace technology comparison

1.Reduce investment

The system does not use hot oil kiln , which saves the fixed investment in this part (e.g., oil furnace body, circulating oil pump, pipe, insulation, valve, high-low oil tank, etc.)
 

2.Powersaving

This system saves the circulation pump, the base power is 45KW/200T/24 hours, the motor 24 hours consumption of electricity is 45X24= degrees
 

3.Maintenance cost

The oil stove is need to change a cycle oil once a year, and the replacement cost is about USD.60-.9The oil pipeline should be cleaned regularly, while the boiling wok is direct heat transfer and does not need to be cleaned.
 

4.Comprehensive utilization rate

Because of this system, using the waste heat utilization, tail smoke emission temperature less than 90 ºC, reduces the cost of coal, and heat conduction oil smoke exhaust temperature is 250 ºC or higher, so the new technology is more energy saving. Built-in dust collecting device, simple structure, no need of power, no need maintenance, recovery of gypsum powder back to the calcining chamber. 2-5 tons of gypsum powder can be received daily, and 2 to 3 yuan($0.32-$0.48) per ton of gypsum powder can be reduced.

5.Quality adjustable

The system adopt FD - chamber boiling furnace technology, gypsum powder under different air temperature, different area, fully dehydration in different stages, make the product in the case of without adding any additives, the setting time can be adjusted in 3-15 minutes and normal consistency of 66% - 75%.
 

6.The installation period is short and the area is small

This system has simple structure, compact, no cumbersome pipe valves and related certificates. Easy maintenance, less land occupy .
 

7.Environmentally friendly

This system USES a three-stage dust removal, cyclone dust collect , the electric dust collect , water bath dust removal or bag dust collector, the discharge of tail smoke more clean. According to the requirements of users can provide users with more complete equipment and environmental protection technology.

 
Technical data

 

1. Successful startup, short adjustment time, 15 days.
2. Natural gypsum and desulfurized gypsum not only can be calcine seperately ,but also 
can calcine  together.
3. Energy conservation, quality stability and controlable .Less passive downtime.
4. The natural gypsum can be controlled accurately , continuous and stable, and non-breakable
5. The equipment should be durable, easy to corrode the place to add protection, low maintenance and low labor intensity
6. The temperature of the cooked powder should be below 80 degrees.
7. Main motor use frequency converter , energy saving.
8. Less dust in the workshop and the control room is clear .
9. Designed production time to complete 200,000 tons of output within 10 months.
10. The equipment conforms to the relevant environmental protection, safety and other national rules , and the effect of dust removal can meet the national standards.
11. Anti-corrosion of the production line: the inside of the dust collector is embalmed, the cyclone is wear-resistant, the coal - fired furnace is scoured, hammer dryers remove iron and cache

 
Technical feature

1 Continuous production: using hammer dryer and soft start, 2 Quality stability: modification mill can increase the specific surface are of materials. 3 Energy conservation and stability: great brand frequency transformer 4 High performance of equipment: using bag dust collector ,water bath desulfurization and denitration treatment, requency transformer,Siemens electrical, PLC, guomao reducer, national standard cable, electrical control: ABB. 5 Easy control: Adpot computer display, PLC control. 6 Mature experience: The core features of our company are mature technologies that can provide a solid foundation for your company.
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The air dryer is used to bake the gypsum powder water containing less than 5% before entering the boiling furnace.this step can increase the gypsum liquidity .when it come to the boiling furnace ,it can easy to calcinate ,so we have this step:Because the chemical gypsum powder has the quality problem, through the modification grinding, changes the chemical gypsum component characteristic, make the quality similar to the natural gypsum powder.The technology of FD - chamber boiling furnace technology can effectively prevent the mixing of raw materials with gypsum powder in the process of calcining .Traditional calcining technologies such as vertical boiling furnace , rotary kiln ,general boiling furnace, etc.Due to the effect of mixing function of the machinery and air flow, dihydrate gypsum ,semi-hydratedgypsum and anhydrite gypsum three-phase blending mutually in the process of boiling dehydration,It is inevitable that the phase composition of the final product will be polyphasic, and the product quality index will be reduced significantly.And FD - chamber fluid bed calcining process changes according to the temperature curve of gypsum powder , artificially divide calcining process into four relatively independent dehydration space, effectively avoid the phenomenon of high and low temperature material blending and the composition of the final product was improved .In the 1 and 2 areas of the main calcining furnace, high temperature heat transfer technology is adopted to rapidly heat and dehydrate the materials that have just entered the FD- chamber boiling furnace, and slowly dehydrate in the 3 and 4 areas.Under the action of high pressure wind, the whole material presents a fluid boiling state, which improves the efficiency of heat transfer and mass transfer in gas and solid powder..The system does not use hot oil kiln , which saves the fixed investment in this part (e.g., oil furnace body, circulating oil pump, pipe, insulation, valve, high-low oil tank, etc.)This system saves the circulation pump, the base power is 45KW/200T/24 hours, the motor 24 hours consumption of electricity is 45X24= degreesThe oil stove is need to change a cycle oil once a year, and the replacement cost is about USD.60-.9The oil pipeline should be cleaned regularly, while the boiling wok is direct heat transfer and does not need to be cleaned.Because of this system, using the waste heat utilization, tail smoke emission temperature less than 90 ºC, reduces the cost of coal, and heat conduction oil smoke exhaust temperature is 250 ºC or higher, so the new technology is more energy saving. Built-in dust collecting device, simple structure, no need of power, no need maintenance, recovery of gypsum powder back to the calcining chamber. 2-5 tons of gypsum powder can be received daily, and 2 to 3 yuan($0.32-$0.48) per ton of gypsum powder can be reduced.The system adopt FD - chamber boiling furnace technology, gypsum powder under different air temperature, different area, fully dehydration in different stages, make the product in the case of without adding any additives, the setting time can be adjusted in 3-15 minutes and normal consistency of 66% - 75%.This system has simple structure, compact, no cumbersome pipe valves and related certificates. Easy maintenance, less land occupy .This system USES a three-stage dust removal, cyclone dust collect , the electric dust collect , water bath dust removal or bag dust collector, the discharge of tail smoke more clean. According to the requirements of users can provide users with more complete equipment and environmental protection technology.1. Successful startup, short adjustment time, 15 days.2. Natural gypsum and desulfurized gypsum not only can be calcine seperately ,but alsocan calcine together.3. Energy conservation, quality stability and controlable .Less passive downtime.4. The natural gypsum can be controlled accurately , continuous and stable, and non-breakable5. The equipment should be durable, easy to corrode the place to add protection, low maintenance and low labor intensity6. The temperature of the cooked powder should be below 80 degrees.7. Main motor use frequency converter , energy saving.8. Less dust in the workshop and the control room is clear .9. Designed production time to complete 200,000 tons of output within 10 months.10. The equipment conforms to the relevant environmental protection, safety and other national rules , and the effect of dust removal can meet the national standards.11. Anti-corrosion of the production line: the inside of the dust collector is embalmed, the cyclone is wear-resistant, the coal - fired furnace is scoured, hammer dryers remove iron and cacheOur Service

Contact us to discuss your requirements of Gypsum powder manufacturing plant. Our experienced sales team can help you identify the options that best suit your needs.