Limestone is the main raw material for burning lime and cement, and also the flux for ironmaking and steelmaking.
Rock structure Limestone structure is complex, including clastic structure and granular structure. The clastic structure is mainly composed of particles, micrite matrix and bright crystal cement. Particles, also known as particles, mainly include internal debris, biological debris and oolitic particles. Mud crystal matrix is gypsum composed of calcium carbonate fine powder or crystals, the particles are mostly less than 0.05 mm, and bright crystal cement is chemical precipitation filled in the pores between rock particles, which is calcite crystal particles with a diameter greater than 0.0 1 mm; Grain structure is crystal particles precipitated by chemical and biochemical actions.
Structure classification Gypsum content/%
Particle content/%
granule
Li Pin
Biological framework
Endoclastic limestone
biology
Oolitic grain
block mass
Fecal particles
Ⅰ granular marl
Ⅰ1granular limestone
10
25
50
75
90
90
75
50
25
10
Internal clastic limestone
Biological limestone
Oolitic limestone
Lumped limestone
Fecal limestone
Ⅱ crystalline limestone
Ⅲ
mineral
Stoneboog
Stoneboog
ash
overhanging cliff
Ⅰ 2 containing stucco particles
limestone
Limestone with debris in mortar
Biogenic limestone containing plaster
Oolitic limestone containing plaster
Limestone containing mortar blocks
Limestone containing gypsum and fecal particles
Ⅰ 3 stucco granular limestone
Clastic limestone in mortar
Mortar biological limestone
Mortar oolitic limestone
Mortar briquette limestone
Mortar manure limestone
Ⅰ 4 granular mortar limestone
Internal detrital stucco limestone
Biomass stucco limestone
Oolitic gypsum limestone
Block plaster limestone
Fecal argillaceous limestone
Ⅰ 5 Limestone with Granular Mortar
Limestone containing internal debris mortar
Limestone containing biological stucco
Limestone containing oolitic mortar
Limestone containing oolitic mortar
Muddy limestone containing fecal particles
Ⅰ 6 stucco limestone
Mortar limestone
(According to East China Petroleum Institute)
Rocks are distributed in limestone produced by biochemical processes and often contain rich organic debris. Limestone generally contains some dolomite and clay minerals. When the content of clay minerals reaches 25%~50%, it is called argillaceous rock. When the content of dolomite reaches 25%~50%, it is called dolomite limestone. Limestone is widely distributed, with uniform lithology and easy to be mined and processed. It is a widely used building material.
Especially in North China and Southeast China, the Middle Ordovician transgression reached the most * * *, and thick and pure limestone was generally deposited, which is the raw material of cement and gold industry and has industrial value.
The main component of limestone is calcium carbonate, which is soluble in water containing carbon dioxide. Generally speaking, a liter of water containing carbon dioxide can dissolve about 50 mg of calcium carbonate.
Calcium carbonate deposited in limestone lakes and oceans, after losing water, closely combines to form rocks, which is called limestone. The mineral composition of limestone is mainly calcite (accounting for more than 50%) and some impurities such as clay and silt. The formation of most limestone is related to biological action. The limestone accumulated by biological relics includes coral limestone, shell limestone and algae limestone. , collectively known as biological limestone. Limestone formed by chemical precipitation of calcium carbonate (CaCO3) in aqueous solution is called chemical limestone. Such as common limestone and siliceous limestone.
Rock limestone is one of the most widely distributed minerals in the crust. According to its sedimentary area, limestone can be divided into marine deposits and continental deposits, with the former accounting for the majority; According to the genesis, limestone can be divided into three types: biological deposition, chemical deposition and secondary deposition. According to the different components contained in the ore, limestone can be divided into siliceous limestone, clayey limestone and dolomitic limestone. Resource distribution: China is rich in limestone mineral resources, with more than 800 limestone deposits used in cement, solvent and chemical industries. The producing areas are all over the country, and all provinces, municipalities and autonomous regions can use local materials near industrial zones.
Limestone limestone minerals are deposited in every geological era and distributed in every stage of geological structure development, but limestone deposits with good quality and large scale often appear in some horizons. Taking limestone for cement as an example, the Middle Ordovician Majiagou Formation limestone in Northeast China and North China is an extremely important horizon, while Carboniferous, Permian and Triassic limestone are widely used in Central South, East China and Southwest China, Silurian and Devonian limestone are widely used in Northwest China and Tibet, and Ordovician limestone in East China, Northwest China and the middle and lower reaches of the Yangtze River is also an important horizon for cement raw materials.
Ore properties 1. Mineral composition of ore The mineral composition of limestone is mainly calcite, accompanied by carbonate minerals such as dolomite and magnesite, and mixed with some other impurities. Among them, magnesium appears in the form of limestone and magnesite, silica is free time, chalcedony and opal are distributed in rocks. Alumina reacts with silica to synthesize aluminum silicate (clay, feldspar and mica). Iron compounds exist in carbonate (magnesite), pyrite (pyrite), free oxides (magnetite and hematite) and hydroxides (hydrous goethite). In addition, there are glauconite. In some types of limestone, there are organic substances such as coal and asphalt, sulfates such as gypsum and anhydrite, compounds of phosphorus and calcium, alkali metal compounds and compounds such as strontium, barium, manganese, titanium and fluorine, but the content is very low.
Limestone 2. Properties of limestone
Limestone has good machinability, polishing and good cohesiveness. Insoluble in water and soluble in saturated sulfuric acid. It can react with various strong acids to generate corresponding calcium salts and release CO2 at the same time. Limestone is decomposed into lime (CaO) and releases CO2 when it is calcined above 900℃ (generally 1000~ 1300℃). When quicklime deliquesces in water, it immediately forms hydrated lime [Ca(OH)2], which can be adjusted after being dissolved in water and is easy to harden in air.
Process characteristics Lime has excellent properties, such as thermal conductivity, firmness, water absorption, air impermeability, sound insulation, polishing, good cementation and machinability, which can not only directly utilize raw ore, but also be further processed and reused.
Main uses Limestone is an important industrial raw material for metallurgy, building materials, chemical industry, light industry, construction, agriculture and other special industrial sectors. With the development of steel and cement industries, the importance of limestone will be further enhanced.
The quality requirements of limestone in quality standards vary according to different uses. Generally speaking, the requirements of special industrial sectors such as metallurgy and chemical industry for limestone purity are higher than those of construction industry and agriculture. Except the People's Republic of China (PRC) (PRC) professional standard ZBD6000 1-85 for limestone used in metallurgical industry, other industries have not formulated national standards or professional standards, but all application departments have formulated relevant standards by themselves. Quality requirements of limestone products in building materials industry
Limestone (1) cement industry: See Table 7 for the quality requirements of calcareous raw materials used in cement production. For amorphous limestone, its particle size is required to be 30 ~ 80 mm
(2) Glass industry: Generally speaking, limestone with different CaO content is selected according to different glass quality requirements, but the limestone required is amorphous and stable in composition.
Comprehensive utilization technology, method and technological process China's limestone resources are characterized by large reserves and good quality. Therefore, large limestone mines in China adopt the method of ore washing-crushing-classification to treat limestone ore, so as to remove the pollution of topsoil, sand and cohesive mud to sandstone. For low-grade limestone or limestone with different ore properties, some foreign countries adopt flotation or photoelectric beneficiation. For example, separating limestone and time from iron by flotation; Separation of limestone and dolomite from magnesite by flotation or photoelectric beneficiation.
Present situation, existing problems and solutions of development and utilization
Limestone limestone has a wide range of uses and is an essential raw material for all sectors of the national economy and people's lives. Mainly used for: (1) cement production and lime burning in the construction industry; (2) Metallurgical industry is used as flux; (3) Used in the chemical industry to make alkali, bleaching powder and chemical fertilizer; (4) Used as clarifier in food industry; (5) used for improving soil in agriculture; (6) Used as filler in plastic industry; (7) It is widely used to make various architectural coatings in the coating industry; (8) Used as alkaline filler in paper industry; (9) Used as the basic filler of rubber in rubber industry; (10) is used as adsorbent in environmental protection industry.
Heavy calcium carbonate is a product with natural calcite, limestone and chalk as raw materials, which is mechanically crushed to a certain fineness. Its production methods include dry method and wet method, and the wet grinding process which has made great progress abroad is still blank in China. In the process of producing light calcium carbonate from limestone, there is still a big gap between the particle size and crystal shape control of light calcium carbonate products and those of foreign countries. Therefore, it is necessary to further develop the limestone deep processing industry, broaden the application fields, strengthen comprehensive utilization, increase the added value of products and improve economic benefits.
Development Trend Limestone is an important industrial raw material in metallurgy, building materials, chemical industry, light industry, agriculture and other departments. With the development of steel and cement industries, the demand for limestone will further increase. The output of cement is huge, that is, more than 1000 billion tons of limestone needs to be mined every year to produce cement products. It is predicted that by 2020, the national cement output will reach 300 million tons, which will require the exploitation of more limestone as raw materials. In addition, there is a great demand for limestone in metallurgical and chemical industries. Therefore, the production and development prospects of limestone industry are broad. In order to make limestone products have greater value-added benefits, developing deep-processed limestone products is also a development direction in the future.
When the lime limestone developed by Shitai is calcined to 1000 ~ 1300℃, CO2 in CaCO3 can be discharged to make quicklime. Quicklime is a white solid, which is refractory and insoluble. When it meets water, it releases heat and absorbs water to generate hydrated lime. The saturated solution of limewater is alkaline, and it is easy to react with CO2 in the air to generate CaCO3 precipitate. Commercially, it can be divided into four categories: high-calcium lime (CaO≥90%), calcareous lime (CaO≥85%), magnesium-calcium lime (MgO≥ 10%) and high-magnesium lime (MgO≥25%).
Slaked lime is calcium hydroxide (slaked lime)
A. molecular formula: calcium hydroxide
Stone Buddha B. Relative molecular weight: 74.08
C. description: fine white powder. The density is 2.24 g/cm. When heated to 580°C, it loses moisture and becomes calcium oxide, and absorbs CO2 in the air and becomes calcium carbonate. Soluble in acid and glycerol, insoluble in water and alcohol.
Uses: Used as additives and softened water in medicine, rubber and petroleum industries. Used in petroleum industry, when added to lubricating oil, it can prevent coking, sludge deposition, neutralization and anticorrosion.
E. main raw materials and specifications: limestone (CaCO3)≥98%.
F. Preparation method and technological process: Lime leaching method is to calcine limestone into calcium oxide in a calcining kiln, then select, dissolve in water, and then purify, dry and screen to obtain calcium hydroxide products. The reaction formula is as follows:
Calcium carbonate = calcium oxide+carbon dioxide (high temperature) calcium oxide +H2O = calcium hydroxide
The process flow is as follows:
Limestone and coke → roasting → selection → digestion with water → precipitation → separation → drying → screening → packaging → calcium hydroxide.
Calcium oxide a. molecular formula: CaO
B. Relative molecular weight: 56.08
C. description: white amorphous powder. The density is 3.25 ~ 3.38g/cm. The melting point is 2580℃, and the boiling point is 2850℃, which absorbs water and carbon dioxide in the air to generate calcium hydroxide and calcium carbonate. Calcium oxide reacts with water (called "digestion") to generate calcium hydroxide and give off heat (the product is strongly alkaline). Soluble in acid, insoluble in alcohol.
D uses: calcium oxide is used in iron and steel, pesticide, medicine, nonferrous metal, fertilizer, leather making, calcium hydroxide production, laboratory drying ammonia gas and alcohol dehydration.
E. main raw materials and specifications: hydrochloric acid (HCl) 35%; Calcium carbonate (CaCO3)98%.
F preparation method and technological process: calcium carbonate calcination method is to react calcium carbonate with hydrochloric acid to generate calcium chloride, neutralize with ammonia water, filter, add sodium bicarbonate, react to generate calcium carbonate precipitate, and then dehydrate, dry and calcine. The reaction formula is as follows: CaCO3+2HCl→CaCl2+CO2+H2O.
Calcium chloride+ammonium dihydrogen → calcium hydroxide+ammonium dihydrogen.
Calcium hydroxide+sodium bicarbonate → calcium carbonate+sodium hydroxide +H2O
CaCO3→CaO+CO2
The process flow is as follows:
Calcium carbonate is added with hydrochloric acid → acidolysis → neutralization in ammonia water → standing for precipitation → filtration → reaction with sodium bicarbonate → dehydration of calcium carbonate → drying → calcination → screening → packaging → calcium oxide.
Light calcium carbonate A. Molecular formula: CaCO3
B. Relative molecular weight: 100.08
C. Properties: white powder, odorless and tasteless, density: calcite type 2.7 1 1g/cm, nepheline type 2.93g/cm. Melting point (110aatm)1289℃ is insoluble in water and alcohol, slightly soluble in aqueous solution containing ammonium salt or carbon dioxide, soluble in dilute acetic acid, dilute hydrochloric acid and dilute nitric acid, and carbon dioxide is released at the same time, showing an exothermic reaction.
D. uses of limestone: it is mainly used as filler in rubber, plastics, papermaking and other industries, and also used as filler in paint and ink. It is also used to produce toothpaste, welding electrodes, organic synthesis, metallurgy, glass, asbestos and linoleum. It is also a neutralizer for industrial wastewater, an antacid for gastric and duodenal ulcers and an antidote for acidosis.
The main reaction formula: Ca(OH)2+CO2→CaCO3+H2O.
Manufacturers: Sichuan Chongqing Songshan Chemical Plant, Guizhou Anshun Glass Chemical Plant, Yunnan Kunming Chemical Plant, Gansu Lanzhou Baiyin Chemical Plant, Henan Jiaozuo No.3 Chemical Plant, Henan Mixian Chemical Plant, Hunan Hengyang No.3 Chemical Plant, Shanghai Xinjiang Chemical Plant, Shanghai Calcium Carbonate Plant, Jiangsu Yixing Lime Plant, Zhejiang Xing Wu Linghu Chemical Plant, Anhui Anqing Chemical Raw Materials Plant, Shandong Zhangdian Hutian Chemical Plant, Zibo Luocun Chemical Plant, Beijing Ore Material Plant, Hebei Tangshan Chemical Plant and Benxi Lime Chemical Plant.
Heavy calcium carbonate (commonly known as single fly powder, double fly powder, three fly powder and four fly powder)
A. Molecular formula: CaCO3
B. Relative molecular weight: 100.08
C. description: white powder, odorless and tasteless. Exposure to air did not change, and the density was 2.7 1g/cm. Melting point1339 C. Almost insoluble in water, slightly soluble in water containing ammonium salt or iron oxide, and insoluble in alcohol. Boil and dissolve when it meets dilute acetic acid, dilute hydrochloric acid and dilute nitric acid. Decomposition into calcium oxide and carbon dioxide by heating.
D. Usage: According to the different grinding fineness, it is divided into four different specifications: single flying, double flying, three flying and four flying, which are used in various industrial departments respectively.
Single fly powder: used to produce anhydrous calcium chloride, which is an auxiliary raw material for the production of sodium dichromate and the main raw material for the production of glass and cement. In addition, it is also used in building materials and poultry feed.
Shuangfei powder: raw materials for producing anhydrous calcium chloride and glass, white fillers for rubber and paint, and building materials.
Sanfei powder: used as filler for plastics, coatings and paints.
Sifei powder: used as filler for wire insulation, rubber molding products and asphalt felt.
E. main raw materials and specifications: limestone (CaCO3)≥90%.
F preparation method and technological process: the crushing method is a product made by crushing, grading and separating lime containing more than 90% CaCO3. The process flow is as follows:
Limestone → crushing → classification → cyclone separation → heavy calcium carbonate manufacturers.
Shandong Qingdao Chemical Fertilizer Plant and Shanghai Stone Powder Plant.
Collection information geological museum, China Collection information:
Photo of limestone collection in geological museum, China (1) Description: Photo of limestone specimen in Xiaobaihuayu, Qiaotou, Benxi, China. Gray; Granular structure; Block structure; The main mineral composition is calcite.
Collection unit: geological museum, China
Photographs of limestone specimens in geological museum, China (II) Description: Photographs of limestone specimens in Du Yun, China. Gray; Granular structure; Block structure; The main mineral composition is calcite.
Collection unit: geological museum, China