Question 2: How is lime made and how did it come from?

Lime is one of the earliest inorganic cementitious materials used by human beings. Because its raw materials are widely distributed. The production process is simple. Low cost and wide application in civil engineering.

I raw materials and production of lime

All natural rocks with calcium carbonate as the main component, such as limestone, chalk and dolomite limestone, can be used to produce lime.

Natural rock with calcium carbonate as the main component is calcined at a proper temperature, and the product with calcium oxide (CaC) as the main component is lime, also known as quicklime.

In actual production, in order to accelerate decomposition, the calcination temperature is often increased to1000 ~1100℃. Due to the large particle size of limestone raw materials or the uneven temperature distribution in the kiln during calcination, lime often contains undercooked lime and overheated lime. Calcium carbonate in immature lime is not completely decomposed, so it lacks cohesive force when used. Quicklime has a dense structure, and its surface is usually covered with a layer of melt, so its solidification is very slow. Because raw materials often contain magnesium carbonate (MgCO3) and quicklime also contains magnesium oxide (MgO), it can be divided into calcareous lime (MgO ≤ 5%) and magnesium lime (MgO >: 5%).

Quicklime is white or gray, and it is often processed into quicklime powder, hydrated lime powder or lime paste for convenience of use. Quicklime powder is a kind of blessing powder made by grinding massive quicklime, and its main component is CaO；. Hydrated lime powder is a kind of powder obtained by slaking massive quicklime with appropriate amount of water, also known as slaked lime, and its main component is Ca (OH) 2. Lime paste is a paste obtained by curing massive quicklime with more water (about 3-4 times the volume of quicklime). Also called lime slurry. Its main component is also Ca(OH)2.

Second, the curing and hardening of lime.

The process in which quicklime (CaO) reacts with water to produce calcium hydroxide is called lime digestion. The calcium hydroxide product produced by the reaction is called slaked lime or slaked lime.

When lime solidifies, it releases a lot of heat, and its volume increases by 1-2.5 times. Calcined lime with high calcium oxide content solidifies faster, and its heat release and volume increase are also more.

Depending on the amount of water added, lime can be solidified into mature lime powder or lime paste. The theoretical water requirement for lime solidification is 32% of the weight of lime. Fine and evenly dispersed hydrated lime powder can be obtained by adding 60% ~ 80% water into quicklime. If you use excessive water for curing, you will get lime paste with a certain consistency. Generally, lime contains calcined lime, which is slow to cure. If the lime slurry is cured after hardening, it will expand and crack due to the expansion caused by curing. In order to eliminate the harm of quicklime, lime should be "aged" for about 2 weeks after curing.

The hardening of lime slurry includes two simultaneous processes: drying crystallization and carbonization. Lime slurry is dried by evaporation or absorption of water, and the pore network in the slurry produces capillary pressure. Make lime particles more compact and gain strength. This strength is similar to that obtained by clay dehydration, and the value is not large, so it will be lost when it meets water. At the same time, due to drying water loss. The calcium hydroxide solution in the slurry is supersaturated, and the calcium hydroxide crystals crystallize, resulting in strength; However, the number of precipitated crystals is small and the strength increases little. In the atmospheric environment, calcium hydroxide will react with carbon dioxide in the air in a humid state to generate calcium carbonate, and release water, that is, carbonization will occur.

The calcium carbonate crystals generated by carbonization cross each other or grow with calcium hydroxide to form a closely intertwined crystal network, which further improves the strength of hardened lime slurry. However, due to the low content of carbon dioxide in the air and the dense structure of calcium carbonate layer formed on the surface, it will hinder the further penetration of carbon dioxide, so the carbonization process is very slow.

Third, the technical performance, quality requirements and application of lime

(A) the technical characteristics of lime

In the lime slurry formed by the slaking of quicklime, lime particles form the colloidal structure of calcium hydroxide, with extremely fine particles (particle size is about 1μm) and large specific surface area (up to 10 ~ 30m2/g). The surface of lime slurry can absorb a thick water film and a large amount of water, so it has strong water retention ability, that is, good water retention. Mixing it with cement mortar to make mixed mortar can significantly improve the workability of mortar.

Lime hardens by drying, crystallization and carbonization. Because of the low content of carbon dioxide in the air, the hard shell of calcium carbonate formed after carbonization prevents carbon dioxide from infiltrating into the interior and moisture from evaporating outward, so the hardening is slow and the strength after hardening is not high. 1: 3 the 28 d compressive strength of lime mortar is only 0 ... >; & gt

Question 3: What's the difference between lime and quicklime? Lime can be divided into quicklime and hydrated lime. The main component of quicklime is calcium oxide (CaO), and white solid is refractory. Limestone with high CaO content is calcined to above 900℃ in a ventilated lime kiln. It is water-absorbent and can be used as a desiccant. People in China often use it to prevent the resurgence of sundries. React with water (release a lot of heat at the same time), or absorb moisture in humid air, that is, mature lime [calcium hydroxide Ca(OH)2], also known as "hydrated lime". Slaked lime is dissolved in one liter of water1.56g (20℃). Its drink and solution are called "lime water", which is alkaline and absorbs carbon dioxide in the air to form calcium carbonate precipitation.

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Question 4: What is calcium? Is it lime soil? The soil with high calcium carbonate content is generally neutral or weakly alkaline.

Question 5: Quicklime Where can I find lime and limestone widely used as building materials and important raw materials in many industries? Limestone can be directly processed into stone and burned into quicklime. Lime includes quicklime and hydrated lime. The main component of quicklime is CaO, which is generally massive, pure white, and light gray or light yellow when containing impurities. After absorbing water or adding water, quicklime becomes hydrated lime, also called hydrated lime, and its main component is Ca(OH)2. Slaked lime is mixed into lime slurry, lime paste, lime mortar, etc. , used as coating and tile adhesive. Cement is made by mixing limestone and clay and calcining at high temperature. Glass is a mixture of limestone, quartz sand and soda ash. And melted at high temperature. Limestone is used as a flux to remove gangue in ironmaking. Quicklime is used as slagging material in steelmaking to remove harmful impurities such as sulfur and phosphorus. Calcium carbide (mainly CaC2) is made by the reaction of quicklime and coke in an electric furnace. Soda soda is made from limestone, salt, ammonia and other raw materials through multi-step reaction (Solway method). Caustic soda is made by the reaction of hydrated lime and soda ash (causticization method). Bleached lime is prepared by the reaction of pure lime and chlorine. Calcium chloride, calcium nitrate, calcium sulfite and other important calcium salts are made by chemical processing of limestone. Hydrated lime can remove the temporary hardness of water and be used as a hard water softener. Limestone is calcined into pure powdered calcium carbonate, which is used as filler for rubber, plastic, paper, toothpaste, cosmetics and so on. Alkaline lime made of lime and caustic soda is used as an absorbent of carbon dioxide. Quicklime is used as a desiccant and disinfectant. In agriculture, quicklime is used to prepare pesticides, such as lime-sulfur mixture and Bordeaux mixture. The application of hydrated lime in soil can neutralize the acidity of soil, improve soil structure and provide calcium for plants. Brush lime slurry on the trunk to protect the trees. Oil is the lifeblood of economic and national strength development. Whoever owns oil will have the development of 2 1 century. It is not only an economic activity to reserve oil and participate in oil futures market trading, but also for the consideration of strategic development goals. Therefore, controlling oil resources is one of the factors leading to the outbreak of the Iraq war. There is an old saying in China that food is the most important thing for the people. Limestone is the grain of cement industry and the lifeblood of cement production. As long as the cement plant produces, limestone is indispensable for a moment. Whoever occupies limestone resources will occupy the development of cement industry. At present, China's cement enterprises are competing for the market, which can also be said to be a dispute over limestone resources. Therefore, large enterprise groups regard the dominant limestone resources as one of the measures to realize their own development strategy. 1. Limestone is a valuable resource with a wide range of uses. Limestone is the trademark name of limestone as a mineral raw material. Limestone is widely used in the history of human civilization because of its wide distribution and easy availability in nature. As an important building material, it has a long mining history. In modern industry, limestone is the main raw material for manufacturing cement, lime and calcium carbide, and it is an indispensable flux limestone in metallurgical industry. After superfine grinding, high-quality limestone is widely used in making paper, rubber, paint, coating, medicine, cosmetics, feed, sealing, bonding and polishing products. According to incomplete statistics, the ratio of limestone consumed in cement production to limestone consumed in building stone, lime production, metallurgical flux and superfine calcium carbonate is 1: 3. Limestone is a non-renewable resource. With the continuous progress of science and technology and the development of nanotechnology, the application field of limestone will be further broadened.

Question 6: What is quicklime in chemistry? Cao's "quicklime"

Calcium hydroxide'' hydrated lime'

Calcium carbonate'' limestone''

There are only three common tests about lime. Remember the three of them.

Question 7: What is the main function of quicklime? Chemical molecular formula: CaO.

Molecular weight: 56.08

Specific gravity: 3.25-3.38

Melting point: 2580℃- boiling point: 2850℃

Properties and uses: the appearance is white (or gray, brownish white), amorphous, and it can absorb water and carbon dioxide in the air. Calcium oxide reacts with water to generate calcium hydroxide and give off heat. Soluble in acidic water, insoluble in alcohol. It belongs to inorganic alkaline corrosive substances, and the national hazard code is 95006.

Used in steel, pesticide, medicine, desiccant, tanning and alcohol dehydration. Generally, quicklime contains quicklime, which solidifies slowly. If the lime slurry is solidified after hardening, it will expand and crack due to the expansion caused by solidification. In order to eliminate the harm of quicklime, lime should be "aged" for about 2 weeks after curing.

Scope of application: it is especially suitable for puffed food, mushrooms, fungus and other local products, as well as products in instruments, medicine, clothing, electronic communication, leather, textile and other industries.

Lime and limestone are widely used as building materials and important raw materials for many industries. Limestone can be directly processed into stone and burned into quicklime. Lime includes quicklime and hydrated lime. The main component of quicklime is CaO, which is generally massive, pure white, and light gray or light yellow when containing impurities. After absorbing water or adding water, quicklime becomes hydrated lime, also called hydrated lime, and its main component is Ca(OH)2. Slaked lime is mixed into lime slurry, lime paste, lime mortar, etc. , used as coating and tile adhesive. Cement is made by mixing limestone and clay and calcining at high temperature. Glass is a mixture of limestone, quartz sand and soda ash. And melted at high temperature. Limestone is used as a flux to remove gangue in ironmaking. Quicklime is used as slagging material in steelmaking to remove harmful impurities such as sulfur and phosphorus. Calcium carbide (mainly CaC2) is made by the reaction of quicklime and coke in an electric furnace. Soda soda is made from limestone, salt, ammonia and other raw materials through multi-step reaction (Solway method). Caustic soda is made by the reaction of hydrated lime and soda ash (causticization method). Bleached lime is prepared by the reaction of pure lime and chlorine. Calcium chloride, calcium nitrate, calcium sulfite and other important calcium salts are made by chemical processing of limestone. Hydrated lime can remove the temporary hardness of water and be used as a hard water softener. Limestone is calcined into pure powdered calcium carbonate, which is used as filler for rubber, plastic, paper, toothpaste, cosmetics and so on. Alkaline lime made of lime and caustic soda is used as an absorbent of carbon dioxide. Quicklime is used as a desiccant and disinfectant. In agriculture, quicklime is used to prepare pesticides, such as lime-sulfur mixture and Bordeaux mixture. The application of hydrated lime in soil can neutralize the acidity of soil, improve soil structure and provide calcium for plants. Brush lime slurry on the trunk to protect the trees.

Seven or eight thousand cement limestone mines have been discovered in China, including 286 proven reserves 1 286, including 257 large-scale deposits, 48 medium-sized deposits1286 small-scale deposits (ore reserves are more than 80 million tons, 40 million to 80 million tons are medium-sized and less than 40 million tons), and * * marble. The reserves are widely distributed in 29 provinces, municipalities and autonomous regions except Shanghai, among which Shaanxi Province has 4.9 billion tons of reserves, ranking first in the country. The rest are Anhui Province, Guangxi Autonomous Region and Sichuan Province (including Chongqing) in turn, with reserves of 3.4-3 billion tons each; Shandong, Hebei, Henan, Guangdong, Liaoning, Hunan and Hubei provinces have reserves of 3-2 billion tons; Heilongjiang, Zhejiang, Jiangsu, Guizhou, Jiangxi, Yunnan, Fujian, Shanxi, Xinjiang, Jilin, Inner Mongolia, Qinghai and Gansu 13 provinces each have 2- 10 million tons of reserves; Beijing, Ningxia, Hainan, * * and Tianjin each have 500-200 million tons of reserves.

Precautions:

1. The shorter the operation time, the better. Put it in a suitable place in the packaging container to seal and absorb moisture.

2, stored in a dry warehouse, moistureproof, avoid contact with acids.

3. Avoid getting wet during transportation, and handle it with care, so as not to damage the packaging and affect the product quality.

4. Don't eat. In case of entrance, drink plenty of water and see a doctor immediately.

Lime can be divided into quicklime and hydrated lime. The main component of quicklime is calcium oxide (CaO), and white solid is refractory. Limestone with high CaO content is calcined to above 900℃ in a ventilated lime kiln. It is water-absorbent and can be used as a desiccant. People in China often use it to prevent the resurgence of sundries. React with water (release a lot of heat at the same time), or absorb moisture in humid air, that is, mature lime [hydrogen ... >; & gt

Question 8: What harm does lime do to people? Lime powder is an alkaline substance. 1: Inhalation into the lungs will have a * * effect on the air bubbles in the lungs, thus promoting the increase of pulmonary secretions and producing physiological reactions such as cough and expectoration. If too much lime powder is inhaled, it may be deposited in the lungs, affecting the function of alveoli and finally affecting the normal respiratory function. 2. Lime powder is an alkaline substance. If it is in direct contact with the skin for a long time, it will cause skin diseases, which is the simplest. If it is quicklime, it can directly burn the skin, because quicklime will have a process of heating and releasing heat after seeing water. Quicklime is very strong, and eggs can be boiled during the exothermic process. Be sure to take protective measures when contacting lime. Don't be careless