One of the materials that you often encounter in construction or life is limestone. So what is limestone? How are they applied and what types are there? This is not something anyone can answer. So let’s find out with us right now.
What is Limestone?
So What is limestone?
Limestones is considered a sedimentary rock. The composition of limestone is mainly calcite mineral, ie calcium carbonate, symbolized as CaCO3.
It is rarely in pure form, but it is often mixed with impurities such as silicon slate, silica, and igneous rocks as well as clay, silt and sand. Some impurities mixed with limestone are clay, sand, mud, bitumen.
The color of limestones is also quite diverse, from white to ash or light green, yellow, even dark pink and black.
Limestone is the main raw material used to produce cement for the construction industry. The cement industry has become the Economic importance of Viet Nam.
According to the scientists measured, limestone has:
- Hardness: 3
- Volumetric weight: 2,600 ÷ 2,800 kg / m3
- Compressive strength: 1700 ÷ 2600 kg / cm2
- Water absorption: 0.2 ÷ 0.5%
Limestone with high silicon elements will have a large hardness but quite brittle and hard. Compared to normal limestone, dolomite limestone has better mechanical properties. Limestones containing more than 3% of clay elements will have poor water resistance.
Some places in Vietnam that have a lot of limestones are Tai Meo mountain, Phong Nha cave, Ha Long bay, Karst delta, Karst cave, karst erosion.
What is limestone used for?
Although compared with granite, limestone is not as hard, but they are more commonly used. The reason is limestones are easier to exploit and process. People often use limestone to make aggregate for concrete or can also be used to spread pavement of cars, train tracks. In some irrigation works, they are also used.
In addition, people also use limestone to make cladding, paving or other architectural structures. In particular, limestone is heavily used in the production of lime and cement.
Limestone is also an important raw material for the production of light powders and the basic chemical raw material is soda. The light powder is used in many industries such as paper, rubber, plastic, foam, toothpaste, cosmetics, paints, pharmaceuticals, etc.
The light powder is a filler with many advantages, it makes Reduce shrinkage and gloss for product surface.
In the rubber and paper industry, light pulp outperforms kaolin in terms of durability and whiteness. In the industry of manufacturing light-duty adhesives are used as fillers due to their good adhesion.
Soda is also one of the essential basic chemicals of the national economy. Soda is used in many industries such as raw materials for washing powder production, production of liquid glass, non-ferrous metal production, cleaning of petroleum products, use in the textile industry, and production of silk. artificial, etc.
So soda production is growing rapidly.
Potential of limestone materials in Viet Nam
Limestone has minerals mainly calcite. The main chemical composition of limestone is CaCO3, in addition to some other impurities such as MgCO3, SiO2, Fe2O3, Al2O3 …
In our country, 125 limestone deposits have been searched and explored with reserves estimated at 13 billion tons and forecast resources of about 120 billion tons. Vietnam limestone is distributed concentrated in the Northern and Southern provinces.
Limestone in Bac Son and Dong Giao is widely distributed and has the greatest potential.
In Hai Duong, limestone is distributed mainly in the area between the Bach Dang and Kinh Thi Rivers. Large-scale mountains such as Han Mountain, Dang Dau Mountain, Nham Duong Mountain have been meticulously explored.
In Hai Phong, limestone is concentrated mainly in Trai Son and Trang Kenh in Thuy Nguyen district. There are also limestone mines scattered in Duong Xuan – Phap Co, Phi Liet, Thiet Khe, Mai Dong, and Nam Quan.
Dolomite limestone is concentrated in the Han Mountain range, Hoang Thach mountain range – Hai Duong with reserves of up to 150 million tons. The limestone geological reserve of Hai Phong area is 782,240 thousand tons of grades A + B + C1 + C2.
The reality of production limestones
The situation of light powder production in Vietnam
Vietnam has more than 10 light powder production facilities.
Hanoi has 2 facilities
Ho Chi Minh City has: 2
Hai Phong has: 2
Phu Ly has: 1
Vinh Phuc has 1
Bac Giang has 1
Lang Son has 1
Light powder production technology is mainly based on CO2 absorption technology. Our light flour products are often highly alkaline and unstable in quality due to outdated and manual equipment processes, without intensive investment in technology regime research.
Although some facilities have improved their equipment in some stages, local and single changes have been less effective.
Even an imported technology line, as well as entire foreign equipment, does not work well because the price of the product is much higher than the price of the product manufactured on a manual line and the product is not. Completely meets the “Advanced Light Powder” standard.
The situation of light powder production in the world from natural limestone
The US, Canada, Europe and Asia are the largest light powder producers and consumers. Mineral fillers in paper products include finely ground calcium carbonate, light powder, kaolin, and titanium dioxide. High-quality natural calcium carbonate is not readily available in North America.
As a result, light pulp production has increased significantly in the North American paper industry’s filler market. Another reason for the increased demand for light pulp in the pulp industry is the use of recycled paper.
Recycled paper fibers are shorter and softer so the whiteness is worse than the original ones, thus requiring a greater amount of high whiteness fillers to raise the whiteness of the paper. The fill level of minerals in pulp can be up to 50%.
North America’s padded formula is 80% kaolin, 20% CaCO3. Currently shifting to a formula of 40% kaolin and 60% light powder.
In addition to the demand for light powders in paper production, there is also the demand for light powders in the manufacture of rubber, plastics, paints, and pharmaceuticals,…
The total production of light flour in North America is 600,000 tons/year. The leading light powder manufacturing companies in North America are Plizer Inc and ECC international Inc. Plizer has 25 light powder manufacturing facilities across the United States.
These light pulp facilities are located in the papermaking area. Slight powder in suspension is transported via pipe to pulp mill. By the end of 1992 Pfizer had a total of light powder production facilities of up to 32 facilities.
Market situation of limestones
The demand for light powders in the domestic fields is as follows:
Plastic production 14%
24% toothpaste and cosmetics
31% rubber Manufacture of 5% battery covers
Our light flour products do not provide enough for domestic needs, moreover, for those requiring high product quality, ours are not satisfactory, so we have to enter annually about 150,000 tons of light powders for domestic use such as paint, plastic, cosmetics, paper, etc.
Producing soda from limestone
Currently, in Viet Nam there is no soda factory, new projects are forming a soda factory with a capacity of 150,000-200,000 tons/year.
The leading chocolate producers in the world are Solvay Company (Belgium), ICI (UK), FMK and Klaid (USA).
Production technology limestones
Soda is produced by several methods:
- Producing by Solvay method.
- Producing from raw materials containing natural soda.
- Caustic soda carbonation method: this method is rarely used.
In fact, most soda factories now use ammonia method, except some countries with natural soda mines such as USA, Kenia, Mexico.
In Japan about 90% of soda production is produced by the improved ammonia method. Producing soda by Solvay method has the following advantages:
- Raw materials are kitchen salt, limestones which are cheap and easy to find.
- Process reactions are carried out at low temperatures (below 100 ° C) and pressures close to atmospheric pressure.
- Stable technology process.
- High-quality products.
- Relatively low price.
This method also has some disadvantages:
- Low utilization of starting materials.
- Waste a large amount of waste that needs to be treated.
- High energy costs.
- Basic investment to build large production facilities.
The material consumption for 1 ton of soda is:
- NaCl salt solution (310g / l) 5m3.
- Ammonia water (25% NH3) 10kg.
- Limestone (100% CaCO3) 1,100kg – 1,400kg (depending on the quality of limestone and production technology equipment)
In Our country, the technology of soda production should follow the Solvay method.
What is burnt-limestone?
Burnt-lime, commonly known as Calcium oxide (CaO) or quicklime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature.
The broadly used term “lime” connotes calcium-containing inorganic materials, in which carbonates, oxides and hydroxides of calcium, silicon, magnesium, aluminum, and iron predominate.
By contrast, quicklime specifically applies to the single chemical compound calcium oxide. Calcium oxide that survives processing without reacting in building products such as cement is called free lime.
It is a white crystalline solid and is a caustic and alkaline substance. As a commercial product, quicklime contains both magnesium oxide (MgO), silicon oxide SiO2 and small amounts of aluminum oxide Al2O3 and iron (II) FeO oxides.
Conventional calcium oxide is produced by thermal decomposition (heating) of natural materials such as limestone which is a mineral containing calcium carbonate (CaCO3).
It occurs when the material is heated to around 900 ° C (American Scientist), a process known as calcining, to remove carbon dioxide in an irreversible chemical reaction.
Lower temperatures can produce a reversible reaction, which allows the material calcined into quicklime to reabsorb the surrounding carbon dioxide to become limestone.
This is one of the reactions that humans have known since the Prehistoric Times.
What is burnt limestone used for?
Uses of burnt limestone for Manufacturing industry :
- Burnt limestone is also used in glass production.
- Burnt limestone works to remove impurities in the production of metals and alloys such as steel, magnesium, aluminum, …
- In the Hygiene industry, burnt limestone works as an effective antifreeze Lime is used to soften as a flocculant and glue.
- Quicklime is a substance used to purify citric acid, glucose, dyes.
Using burnt limestone for wastewater treatment
- Quicklime is used in water and wastewater treatment to reduce acidity or to remove impurities such as phosphate and other impurities.
- Lime is in pollution control – in steam filters that are used to remove sulfur-based emissions and process many liquids.
Uses of quicklime for pottery making:
- Lime is a basic flow aid for medium and high-temperature enameled glazes, it starts to work at about 1100 ° C.
- Quicklime usually makes the post-baked glaze harder, has better resistance to scratches and acid corrosion.
- Lime is often used to reduce the viscosity of enamel with high silica content.
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