The original lime production process is to lay the limestone and fuel (wood) in layers and draw fire calcination for a week that is obtained. In modern times, mechanized and semi-mechanized vertical kilns and rotary kilns, boiling furnaces and other equipment are used for production. Calcination time is also correspondingly shortened, with the rotary kiln production of lime only 2 to 4 hours, than with the production of vertical kilns can improve productivity by more than 5 times. In recent years, and the emergence of cross-flow type, double slope type and oil burning ring row kiln and short rotary kiln with preheater and other energy-saving process and equipment, the fuel is also expanded to coal, coke, heavy oil or liquefied petroleum gas and so on.
3. Raw materials and production
Any natural rock with calcium carbonate as the main component, such as limestone, chalk, dolomitic limestone, etc., can be used to produce lime.
The main component of calcium carbonate of natural rocks, calcined at the appropriate temperature, excluding the decomposition of carbon dioxide, the resulting calcium oxide (CaO) as the main component of the product is lime, also known as quicklime.
In actual production, in order to speed up the decomposition, the calcination temperature is often increased to 1000 ~ 1100 ℃. Due to the size of the limestone raw materials or calcination in the kiln temperature distribution is not uniform and other reasons, lime often contains underfire lime and overfire lime. Underfire lime in the calcium carbonate is not completely decomposed, the use of a lack of adhesion. Overfire lime structure is dense, the surface is often covered with a layer of molten material, maturation is very slow. Due to the production of raw materials often contain magnesium carbonate (MgCO3), so quicklime also contains a minor component of magnesium oxide (MgO), according to the magnesium oxide content, quicklime is divided into calcareous lime (MgO ≤ 5%) and magnesian lime (MgO & gt; 5%).
Lime is white or gray block, for ease of use, block lime often need to be processed into lime powder, lime powder or lime paste. Lime powder is a block of quicklime ground fine and fine powder, its main component is CaO; lime powder is a block of quicklime with the right amount of water to get the powder, also known as slaked lime, its main component is Ca (OH) 2; lime paste is a block of quicklime with a larger amount of water (about 3-4 times the volume of quicklime) cooked and get the paste. Also known as lime slurry. Its main ingredient is also Ca(OH)2.
4. Cooking and hardening
Lime (CaO) reacts with water to produce calcium hydroxide, known as the process of lime ripening or digestion. The product of the reaction, calcium hydroxide, is called slaked lime or quicklime.
Lime ripening releases a lot of heat, the volume increases 1-2.0 times. Calcined good, high calcium oxide content of lime ripening faster, the amount of heat and volume increase is also more. Site on the lime cooked commonly used two methods: slaked lime slurry method and slaked lime powder method.
Depending on the amount of water added, lime can be cooked into slaked lime powder or lime paste. Theoretical water requirement for lime ripening is 32% of the weight of lime. In quicklime, uniformly add 60% to 80% of water, you can get fine particles, evenly dispersed lime powder. If cooked with excess water, lime paste with a certain consistency will be obtained. Lime generally contains overcooked lime, overcooked lime is slow to mature, if the lime paste hardens and then occurs after maturation, it will cause bulging and cracking due to the expansion produced by maturation. In order to eliminate the hazards of overcooked lime, lime in the cooked, should also be "Chen Fu" about 2 weeks.
Hardening of lime slurry includes drying crystallization and carbonization of two simultaneous processes. Lime slurry due to water evaporation or absorption and drying, in the pore network within the slurry, resulting in capillary pressure. Strength is gained by making the lime particles more compact. This strength is similar to the strength gained by loss of water in clay, which has a small value and is lost when exposed to water. Also, due to drying water loss. Causes supersaturation of the calcium hydroxide solution in the slurry, which crystallizes calcium hydroxide crystals and produces strength; however, the number of crystals precipitated is small, and the increase in strength is not great. In the atmospheric environment, calcium hydroxide in the humid state will react with carbon dioxide in the air to produce calcium carbonate and release water, that is, carbonization occurs.
The calcium carbonate crystals generated by carbonation are cross-linked with each other or with calcium hydroxide***, forming a tightly interwoven crystalline network, so that the strength of the hardened lime slurry is further improved. However, due to the low carbon dioxide content in the air, the calcium carbonate layer formed on the surface of the structure of the denser, will hinder the further infiltration of carbon dioxide, therefore, the carbonization process is very slow. Lime slurry formed after lime maturation, lime particles form a calcium hydroxide colloidal structure, the particles are very fine (particle size of about 1 μm), the specific surface area is very large (up to 10 ~ 30 m2 / g), its surface adsorption of a thicker layer of water film, can be adsorbed a large amount of water, and thus has a strong ability to maintain water, that is, good water retention. It can be mixed into cement mortar to form mixed mortar, which can significantly improve the compatibility of mortar.
Lime rely on dry crystallization and carbonation and hardening, due to the low carbon dioxide content in the air, and carbonation after the formation of calcium carbonate crust to prevent carbon dioxide to the internal infiltration, but also to prevent the water from evaporating outward, and thus slow hardening, hardening of the strength is not high, 1: 3 of the lime mortar 28 d compressive strength is only 0.2 ~ 0.5 MPa. In the wet environment, lime, water does not evaporate, carbon dioxide in the mixed mortar, can significantly improve the ease of mortar. In a humid environment, the water in the lime does not evaporate, carbon dioxide can not penetrate, hardening will stop; coupled with calcium hydroxide is soluble in water, has been hardened lime will dissolve in the presence of water collapse. Therefore, lime should not be used in long-term humidity and water-soaked environment.
Lime in the hardening process, to evaporate a large amount of water, causing significant volume contraction, easy to appear drying cracks. Therefore, lime should not be used alone, generally mixed with sand, paper tendons, hemp knife and other materials to reduce shrinkage, increase tensile strength, and can save lime.
Lime has a strong alkaline, at room temperature, can react with glassy reactive silicon oxide or reactive alumina to generate a product with water-hardening, resulting in cementation. Therefore, lime is also an important raw material in the building materials industry. Lime in the production of cementitious components are effective calcium oxide and magnesium oxide, the content of which is the main indicator for evaluating the quality of lime. Lime in the effective calcium oxide and magnesium oxide content can be measured directly, but also through the total amount of calcium oxide and magnesium oxide and carbon dioxide content reflects, quicklime and undigested residue content requirements; lime powder has the fineness of the requirements; lime powder and volume stability, fineness and free water content requirements.
The national building materials industry divides construction quicklime, construction lime powder and construction lime powder into three grades of superior and qualified products. However, in the transportation sector, JTJ 034-2000 "Technical Specification for Highway Pavement Subgrade Construction" still divides quicklime and slaked lime into three grades according to the original national standard (GB1594-79). Lime in civil engineering has a wide range of applications, the main uses are as follows:
(1) lime milk and mortar Lime powder or lime paste mixed with a large number of stucco. With lime paste or lime powder can be prepared lime mortar or cement-lime mixed mortar for masonry or plastering works.
(2) lime stabilized soil will be mixed with various kinds of lime powder or raw lime powder crushed or originally loose soil, after mixing, compaction and maintenance of the mixture obtained, known as lime stabilized soil. It includes lime soil, lime stabilized gravel soil, lime gravel soil and so on. Lime stabilized soil has certain strength and water resistance. It is widely used as the foundation of buildings, the bedding layer of the ground and the base layer of roads.
(3) silicate products with lime (lime powder or lime powder) and siliceous materials (sand, fly ash, volcanic ash, slag, etc.) as the main raw materials, after batching, mixing, molding and maintenance can be made after the brick, block and other products. Because the internal cementing material is mainly hydrated calcium silicate, so it is called silicate products, commonly used gray sand bricks, fly ash bricks and so on. ("Ben Jing")
Synonyms chalk ash ("Ben Jing"), xi ash ("Bie Lu"), stone chalk (Tao Hongjing), dyeing ash, scattered ash, white ash, taste ash ("Shi Yao Er Ya"), wrought stone ("Rihua Zi Materia Medica"), stone forging ("Materia Medica"), mineral ash ("Compendium").
Source is limestone calcined by heating.
Mineral form limestone
Mainly composed of calcite, a dense mass. It has a dull, earthy or stony luster. The color varies greatly, depending on the type and amount of impurities it contains. Transparency is also poor. Very dense more shell-like fracture.
Medicinal herbs
①Lime
It is an irregular lump, white or grayish white, opaque. Hard texture. Powder white. Soluble in acid, slightly soluble in water. Exposed to the air to absorb moisture, then gradually weathered and mature lime.
② slaked lime
Also known as: slaked lime. White or off-white powder, occasionally see lumps.
Chemical composition
The main component of limestone is calcium carbonate, common inclusions are silicate, iron, aluminum, magnesium and so on. Limestone plus high heat, then carbon dioxide occurs and left calcium oxide, that is, quicklime (lime). When quicklime meets water, it becomes slaked lime, which is composed of calcium hydroxide. Lime or slaked lime exposed to the atmosphere, constantly absorbing atmospheric carbon dioxide into calcium carbonate; therefore, lime aged, the composition of all become calcium carbonate.
The flavor is pungent, warm, poisonous.
①Benjing: pungent flavor, warm.
② "Shu Ben Cao": toxic.
3 "Rihuazi Materia Medica": taste sweet, non-toxic.
Categorized as ① "Materia Medica Seeking Truth": into the liver, spleen.
② "Materia Medica Summary": into the hands and feet Taiyin, syncope meridian.
Functions and Indications: drying dampness, killing worms, stopping bleeding, stabilizing pain, etching evil flesh. Treatment of scabies, wet sores, trauma bleeding, soup and fire burns, hemorrhoids, prolapse of the anus, warts. Internal use to stop diarrhea and dysentery, disintegration.
①Benjing: main gangrenous ulcers and scabies, hot gas, sores, mange, dead muscles, fall eyebrow, kill hemorrhoids, remove black polyps.
② "Other Records": treatment of gangrene of the medulla oblongata.
3 "Pharmacognosy": knowledge of scabies, etching of flesh, not into the soup, stopping the blood of gold sores, and chicken in the white, the defeat of the ship Ru very good.
4 "Rihuazi Materia Medica": muscle growth, stop bleeding, and the main purpura, scrofula ulcers, scar blemishes, etc., treatment of cold, hemorrhoids, fistulas and gangrenous sores, gall tumors and warts. And cure postpartum yin can not close, thick decoction fumigation. Cure alcohol poisoning, warm water dirty.
⑤ "Compendium": dispersing blood and pain, stopping water and diarrhea of blood and flesh, leucorrhea and white prostitution, collection of anus and anus yin straightening, eliminating the accumulation of tuberculosis, sticking to the mouth to drink, black beard and hair.
6 "Compendium of Medical Sciences": diarrhea of the heart and kidney, break the stasis and attack the accumulation of stagnant blood, astringent lungs and clear the gold, kill insects and detoxification.
Usage and dosage for external use: grinding and mixing compresses, or dissolved in water to clarify the application of washing. Internal use: add into pills, powder, or dissolve with water to take clarified liquid.
Selected prescriptions
①Scabies: wash with lime juice. ("Sun real food taboos")
② summer prickly heat and heat sores: kudzu powder one (three) two, lime one or two (slightly fried), licorice two two (raw for the end). The above medicines and, research to make uniform, with the sheep pouncing. ("Sheng Hui Fang")
3 cure stroke rash: lime with how much and vinegar syrup water mixing coating. (Yuan Xisheng secret prescription)
4 treatment of traumatic hemorrhage: two taels of lime, ice chips two money, alum two money (calcined). Lime fried yellow, add ice chips and alum, research into fine powder, sprinkle on the wound bandage can be. (Xuzhou City, "single prescription new medical method selection")
5 treatment of hemorrhoidal disease, anus side of the swelling hard, itching and pain intolerable: the weathering of lime three two, coriander three two, the stove within the black coal two two, the above medicine pounded Luo for the end, divided into two minutes in the choshi point of vinegar frying, Hou Ting hot, to the wrap ironing of the silk, cold is then replaced. ("Sheng Hui Fang")
6 treatment of the large intestine for a long time accumulation of virtual cold, every time because of the stool de-analization, can not be income: lime boil to make hot, to the old silk wrapped, sitting on it, cold that is, change. ("Sheng Hui Fang")
7 cure partial fall gas pain: Chen lime (fried), five times, gardenia and other points. For the end, face and vinegar mixing compress. (Abstract of medical prescription)
⑧ to warts: bitter wine impregnated lime six, seven days, take the juice drop point warts on. ("Thousand Gold Formula")
9 mumps swelling and pain: vinegar and lime. ("Simple single formula")
⑩ treatment of phlegm core redness, swelling, cold and heat, like scrofula: lime calcined for the end of the white fruit flesh with the paste, honey can also be adjusted. ("living people heart system")
11 treatment of furuncles: lime three points, two points of the horse's teeth vegetable. The above two flavors pounded, with chicken seeds and white and compress. ("Thousand Gold Formula")
(12) treatment of dysentery and blood for decades: three large liters of lime, fried to make yellow, stirred with a bucket of water, so that the clarification, a service of one liter, three services. ("Wai Tai")
(13) treatment of leucorrhoea and watery diarrhea: weathered lime one or two, white poria three two. For the end, paste the pill sycamore size. Each serving two, thirty-nine, empty heart under the rice drink. ("Jixuan Fang")
(14) treatment of abdominal coercive accumulation of blocks: weathering lime half a catty, wares fried very hot, into the rhubarb end one or two, fried red to take up, into the cinnamon end of half a two, a little burned, into the rice vinegar and into a paste, spread on the silk paste, internal consumption of elimination of blocks of medicine, very effective. (Danxi Xinfa)
Clinical application
①Treatment of chronic bronchitis
Take 0.5 pounds of lime, add 5 pounds of clean water, stir and precipitate for 24 hours, take the supernatant, filter. Take 3 times a day, each time 20-30 ml. Or take 0.5 catty of scutellaria, decoct twice and remove the dregs, concentrate the liquid to about 200 milliliters, add to the lime liquid to make 2000 milliliters, the content of scutellaria is about 10%. Taken 3 times a day, each time 20-30 ml.
②Treatment of lower limb ulcers
Take the old lime to remove the floating dirt after research Wei fine powder, spread the wound. When using the first to clean the wound; medication and then use boric acid ointment dressings outside. If the wound is wet and dripping, single powder can be used. For a long time does not close the mouth of the trauma, broken frostbite, burns, etc. also have efficacy.
3 treatment of burns
Take lime 1 catty into the basin, add cool water 1250 ml, to be lime moisture into a paste, the basin will be gently oscillated to make the bottom of the lime, take the upper layer of dregs of the lime milk about 500 grams, add 8 egg whites stirred into a jelly-like, and then add 60 milliliters of sesame oil, mixing that is the cream of lime.
When using the first tweezers to the injured surface of the floating skin pull flat, blisters and scabs do not move, but also do not use any liquid disinfection; take more than the injured surface of the gauze 3 to 4 layers, spread 1 to 1.5 cm thick lime cream, pasted on the injured surface, bandage fixed, loose and tight. 48 hours after the ointment that is solidified and shaped. If the injury in the neck, armpit, popliteal fossa, the drug to be thick, bandaged within 48 hours after the injury, do not flex, in order to prevent the cream off, the skin adhesion. 10 ~ 15 days to remove the gauze and lime cream, blisters can be seen to be absorbed, the scabs fall off on their own. For the burn area is large, the injured surface has been infected patients, to control the infection in time, to prevent shock, to maintain the balance of water and electrolytes.
④Treatment of ringworm
Take half a bowl of freshly weathered lime, add water to 1 bowl, stir and then precipitate for 3 minutes, take the upper layer of emulsion, add about 4 drops of tung oil, stir vigorously, and then remove the excess water to make the paste, and then externally apply to the affected area. The treatment of more than 60 cases, generally only a few times to see the effect.