Lead is a metallic chemical element with the symbol Pb, atomic number 82 and atomic weight 207.2. It is a non radioactive element with the largest atomic weight.Metal lead isface-centered cubic crystal 。[1]
Lead metal is corrosion resistantHeavy non-ferrous metalsMaterials: lead has the advantages of low melting point, high corrosion resistance, X-ray and gamma ray penetration resistance, good plasticity, etc. It is often processed into plates and pipes, and is widely used in chemical, cable, battery, radioactive protection and other industrial sectors.[1]
On October 27, 2017, the list of carcinogens published by the International Agency for Research on Cancer of the World Health Organization (WHO) was preliminarily sorted out for reference, and lead was included in the list of Category 2B carcinogens.[22]
On July 23, 2019, lead was included in the list of toxic and harmful water pollutants (the first batch)[2]。
Lead (Pb) is a kind of high-density, soft blue gray metal, with a melting point of 327 ℃ and a boiling point of 1740 ℃[1]When the temperature exceeds 400 ℃, a large amount of lead vapor will escape and rapidly oxidize into lead oxide smoke in the air.Common lead containing substances include Mitha Lama (PbO), Huang Dan (PbtwoOthree）, lead (PbthreeOfour）Lead white (Pb (OH)two·2PbCOthree）, lead sulfate (PbSOfour）Etc.In nature, galena (PbS) and white lead ore (PbCOthree）Exists in the form of lead alum (PbSOfour）There is also natural lead occasionally.Lead ore is often mixed with zinc, silver, copper and other elements.Lead and its compounds are widely used, and can be contacted in metallurgy, storage battery, printing, pigment, paint, glaze, soldering tin and other operations.[4]
The crystal structure of lead is cubic lattice.Lead has high density, low hardness, low melting point, high boiling point, poor conductivity to electricity and heat, and can absorb radiation, so it is used to manufacture containers for radioactive substances and as protective materials.[5]
This metal has strong corrosion resistance, and some lead pipes installed by the ancient Romans are still intact.Lead is mostly used in pipes (although it has now been replaced by plastic).Lead is also used to block X-rays, make munitions, act as a jacket for cables, crystal glass (as lead oxide), and as an antiknock agent (such as tetraethyl leadtwoHfive)fourPb)。Most lead salts are insoluble in water, only nitrate (Pb (NOthree)two）And acetate (Pb (CHthreeCOO)two）Exceptions.Severe lead poisoning can cause diarrhea and vomiting, but lead poisoning is usually chronic, with symptoms of abdominal pain, muscle pain, anemia, and nerve and brain damage.Children are particularly vulnerable to excessive lead inhalation from vehicle exhaust.[6]The daily average maximum allowable concentration of lead in the atmosphere of the residential area is 0.00007mg/mL, and the maximum allowable concentration in the surface water is 0.1mg/L.[4]
Physical and chemical properties
Lead is located in the sixth cycle Ⅳ A group, with atomic radius of 146pm, Pb radius of 84pm, first ionization energy of 718.96kJ/mol, electronegativity of 1.8, and main oxidation numbers of+2 and+4.The silvery gray shiny heavy metal is easy to oxidize in the air and lose its luster, becoming gray, soft, weak ductility and strong ductility.Density 11.34g/cmthree, melting point 327.5 ℃, boiling point 1740 ℃[3]。It has strong resistance to radiation penetration.
PlumbicRecrystallization temperatureUnder room temperature, the pressure workability is excellent, and no work hardening occurs.The strength and hardness of lead and lead alloys, especially the low fatigue strength and creep strength, are easy to be damaged by fatigue and creep. Attention should be paid when designing and using them as components.[1]
Main physical and mechanical properties of lead
performance
data
Density (20 ℃)/g · cm-3
eleven point six eight
Melting point/℃
three hundred and twenty-seven point four
Boiling point/℃
one thousand seven hundred and forty
Average specific heat capacity (0~100 ℃)/J · (kg · K)-1
one hundred and twenty-nine point eight
Melting heat/kJ · mol-1
four point nine eight
Gasification heat/kJ · mol-1
one hundred and seventy-eight point eight
Thermal conductivity (0~100 ℃)/W · (m · K)-1
thirty-four point nine
Resistivity (20 ℃)/μΩ· cm
twenty point six
Tensile strength/MPa
fourteen point seven
Elongation/%
60~70
Brinell hardness/MPa
30~48[1]
There are four stable isotopes of lead: Pb-204（abundance1.4%), Pb 206 (24.1%), Pb 207 (22.1%) and Pb 208 (52.4%).The last three are the final products of uranium-238, uranium-235 and thorium-232 after a series of fission. Only Pb is a naturally occurring, non decaying product.[7]Pb 208 has the largest mass among stable isotopes.
Chemical activity
At room temperature, a layer of lead oxide orBasic lead carbonateTo tarnish the lead and prevent further oxidation.It is easy to combine with halogen and sulfide to generate PbClfour、PbItwo, PbS, etc.Molten lead produced by air reactionLead monoxide, heating lead in pure oxygenLead dioxide。React with hydrochloric acid to release hydrogen and generate slightly soluble PbCltwo, covering the lead surface to stop the reaction.Reaction with hot concentrated hydrochloric acid to generate HPbClthreeAnd Htwo。AndDilute sulfuric acid reactionHydrogen is released and insoluble PbSO is generatedfourCover layer to stop the reaction.But it is easily soluble in hot concentrated sulfuric acid to generate Pb (HSOfour)twoAnd release SOtwo。React with dilute nitric acid or concentrated nitric acid to form lead nitrate Pb (NOthree)two。It can be dissolved in acetic acid and other organic acids under aerobic conditions to generate soluble lead salts.React slowly with strong alkali solution to release hydrogen to form lead sulfite.[8]React with water in the presence of oxygen to form insoluble Pb (OH)two。
Lead is initially oxidized to PbO during heating and meltingtwo, continue to heat up and decompose into PbO, and generate Pb when the temperature rises to 603 ～ 723KthreeOfour(i.e. lead).PbtwoOthreeOr PbthreeOfourStable PbO is easily dissociated at high temperature.[5]
Lead in SOtwoIt is very stable, and the lead is hardly mixed with pure COtwoThe corrosion of ordinary water to lead is very slight.Lead is easily soluble in nitric acid, borofluoric acid, silicofluoric acid and acetic acid, but hardly soluble in sulfuric acid, hydrochloric acid and hydrofluoric acid at room temperature.NHfourOH solution or dilute NaOH solution with air can slowly dissolve lead.Lead is soluble inSilver nitrate solutionOther nitrates and chlorides will corrode lead.The sulfate of potassium, sodium, iron and ammonia and the carbonate and cyanide solution of potassium have no effect on lead.[5]
Corrosion resistance mechanism
The surface of lead in the air forms a dense lead oxide filmcarbon dioxideThe lead carbonate film is formed in the air and the lead sulfate film is formed in sulfuric acid. These films play a good role in protection.Therefore, lead has excellent corrosion resistance in many media, especially in sulfuric acid.The corrosion rate in the atmosphere of the lead industrial zone is 0.00043~0.00068mm/a;The corrosion rate in natural seawater is 0.01~0.015mm/a;When the concentration of sulfuric acid reaches 70%~80% and the temperature is 50 ℃, the lead still has good corrosion resistance.[1]
Production method
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Lead smelting raw materials
The crustal abundance of lead is smaller than that of copper, zinc and tin.The main lead ore in nature is sulfide ore, followed by lead oxide ore.Lead sulfide ore is mainly composed of primary galena (PbS).However, there are few single lead sulfide ores, which are often associated with sphalerite and collectively called lead-zinc ores.additionalAssociated mineralsChangyou argentite (AgtwoS）、Pyrite (FeStwo）Chalcopyrite (CuFeStwo）, FeAsS, BitwoSthree）And minerals of indium, germanium, gallium, thallium, tellurium and other rare and scattered elements.Lead zinc ore has complex composition and should be smelted after beneficiation and enrichment in advance.Lead oxide mainly consists of white lead ore (PbCOthree）And lead alum (PbSOfour）It is a secondary ore, mostly appearing in the upper layer of sulfide ore or coexisting with sulfide ore.Lead containing waste and miscellaneous materials are also important resources for lead production.[5]
Extractive metallurgy
Lead extraction metallurgy includes pyrometallurgy and hydrometallurgy. The former is more widely used in industrial production.The traditional pyrometallurgical methods generally include sintering and roasting of lead concentrate, lead smelting, pyrometallurgical refining of crude lead or (electrolytic refining of lead).The blast furnace reduction smelting method is the most widely used traditional lead smelting method.The lead produced by this method accounts for 85% of the total lead production.Lead smelting by blast furnace reduction smelting method is a method of reducing lead oxide into crude lead with coke as reducing agent. This method needs to first convert most of PbS in lead sulfide concentrate into PbO through sintering roasting, and then sinter the sinter into blocks.The crude lead produced by lead smelting also contains many impurities. Only through pyrorefining or electrolytic refining can refined lead meet the product quality standards and user requirements, and valuable metals in the crude lead be recovered.Pyro refining of crude lead plays a leading role in today's lead refining.[5]
The traditional pyrometallurgy has many problems, such as serious environmental pollution, difficult recovery of sulfur in raw materials, high energy consumption and low production efficiency. Since the 1950s, some countries in the world have competed to study direct lead smelting to replace the traditional pyrometallurgy.By the 1990s, industrial production or semi industrial tests had been carried out, including KIVCET-CS, QSL, ISA and flash smelting.The common feature of these direct lead smelting methods is that they do not need to go through separate sintering and roasting treatment, and basically realize self heating smelting. The flue gas is convenient for acid making, and has less environmental pollution. From the perspective of development, it is possible to replace the traditional pyrometallurgical lead smelting method.[5]
Smelting status
(1) Transformation of Lead Smelting Technology
With the continuous development of China's industry, the demand for lead products is increasing.However, due to the limitation of lead smelting technology in China, the supply of lead products is far from the actual demand for lead products.This requires further improvement of China's lead smelting technology. With the continuous progress of smelting technology and the accumulation of practical experience, China's lead smelting technology has been improved to a certain extent. Lead production enterprises are reforming lead smelting technology to further improve the output and quality of lead products.In the production process of lead products in China, the production of lead products is being transformed to the mode of bottom blowing furnace+side blowing reduction furnace+fuming furnace.The transformation of lead product smelting technology not only greatly improves the output and quality of lead products, but also reduces the energy consumption in the lead smelting process, further improving the energy utilization rate.It is believed that with the continuous progress of lead smelting technology, the supply of lead products in China will gradually meet the needs of China's industry for lead products.[9]
(2) Existing problems
The problems existing in the lead smelting process in China restrict the progress of lead smelting technology in China, thus affecting the supply of lead products in China.The problems existing in the lead smelting process in China are mainly divided into three aspects.First of all, China's lead resources are relatively scarce, restricting the supply of lead products in China.As far as the distribution of lead resources in China is concerned, although lead resources are widely distributed, the reserves of lead resources are relatively low, which cannot provide sufficient raw materials for lead smelting.In addition, the waste of lead products in the smelting process is relatively serious, and the energy consumption is large, which also makes the lead resources not fully utilized, thus making the supply of lead unable to meet the demand.Secondly, China's lead smelting supervision is not strict, leading to serious waste of lead resources.[9]
In the production process of lead products in China, the relevant departments did not pay attention to the supervision of lead smelting. On the one hand, some enterprises failed to produce lead products according to production standards, resulting in a waste of lead resources.On the other hand, due to insufficient supervision, lead production enterprises often pay little attention to energy consumption and environmental pollution, resulting in energy waste.At the same time, the pollution in the production process of lead products has caused damage to the environment.In addition, due to insufficient supervision, some enterprises use backward smelting technology to meet foreign demand for lead products, which further aggravates China's resource shortage and environmental pollution.Finally, the environmental pollution caused by the lead smelting process has increased the environmental pressure in China.Due to the restriction of China's lead smelting technology level, dust and waste gas will be produced in the production process of lead products. These dust and waste gas have not been properly disposed, resulting in serious environmental pollution in the production process of lead products.[9]
In the production process of lead productssulfur dioxideSulfur dioxide will lead to acid rain, cause great damage to crops and buildings, and cause economic losses.The pollution caused in the lead smelting process also restricts the supply of lead products.[9]
smelting technology
(1) Oxygen top blowing smelting technology
ISA method and Ausmelt method belong to oxygen top blowing method, and ISA method is taken as an example to further explain the technical characteristics of oxygen top blowing smelting technology.Isa method is different from Kiefset method. It has low requirements for furnace charge, but the smoke and dust rate of this method is high.Another advantage of Isafa is that the furnace equipment occupies a relatively small area, which can save space for lead smelting, reduce the cost of lead smelting to a certain extent, and increase the economic benefits of the enterprise.[9]
(2) Oxygen bottom blowing smelting technology
QSL method and SKS method are both bottom blown molten pool smelting technology, and QSL method is taken as an example to further explain the technical characteristics of oxygen bottom blown smelting technology.QSL method is the same as ISA method. The soot rate is high, and the furnace equipment area of QSL method is relatively small, which can save space for lead smelting, reduce the cost of lead smelting to a certain extent, and increase the economic benefits of enterprises.[9]
(3) Oxygen side blowing smelting technology
Oxygen side blowing smelting technology is a direct lead smelting technology developed in China.The equipment required for this technology is relatively simple and the amount of investment is relatively small.The metal recovery rate is also very high, creating good economic benefits.However, this technology can not control the heat dissipation well, which leads to great energy consumption in lead smelting.The technology has been widely used in China because of its low cost.However, the widespread use of this technology has also caused great pressure on China's energy resources, which is not conducive to sustainable development.This is the problem that our country must solve next for this technology.[9]
Main compounds
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There are many kinds of lead compounds. The main compounds with industrial value are PbS, PbO, PbSOfourAnd lead chloride.[5]
Lead monoxide
Chinese name
Lead monoxide
alias
Also called yellow lead oxide;Commonly known as Huang Dan or Mitha Monk
chemical formula
PbO
Formula quantity
two hundred and twenty-three point one nine
melting point
888℃
density
9.53g/cmthreeAmorphous ones are yellow to reddish yellow, with density of 9.2 ～ 9.5g/cmthree
appearance
There are many variants, tetragonal crystal is yellow red;Diagonal orthorhombic crystal is yellow[10]
Solubility
Lead monoxide is insoluble in water and ethanol, soluble in nitric acid and acetic acid to generate corresponding lead salt, and soluble in hot strong alkaline solution to generate lead sulfite[10]
Chemical activity
Lead monoxide can absorb carbon dioxide in the air to form lead carbonate, which can be formed when heated to 500 ℃ in the airLead tetroxide。It can be heated by carbon, hydrogencarbon monoxideIt is reduced to lead and mixed with glycerol to form a hard substance, which can be used as adhesive.[10]
Preparation method and use
Lead monoxide is usually produced by oxidizing molten lead in air or decomposing heated lead carbonate and lead nitrate. It is often used as a drying agent for pigments, coatings and paints, metallurgical flux, and also used to make special lead glass, enamel, battery electrode, and rubber.[10]
1114 ℃, partial volatilization starts at 860 ℃[11]
Solubility
Insoluble in water and alkali solution.Soluble in nitric acid[11]
Chemical activity
Burning in air can produce lead monoxide and sulfur dioxide[11]
Preparation method and use
Generally, hydrogen sulfide is introduced into acid lead nitrate solution for manual preparation of lead sulfide.The main ore of lead sulfide in nature is galena, which is the raw material for lead smelting.The purified lead sulfide can be used as semiconductor.[11]
Lead chloride
Lead chloride mainly includes PbCltwoAnd PbCl4，PbCl in lead chloridetwoMost important.
Lead dichloride
Lead tetrachloride
appearance
White crystal, toxic
Yellow volatile oily liquid, toxic
alias
-
High lead chloride
molecular weight
two hundred and seventy-eight point one one
three hundred and forty-nine point zero one
relative density
five point eight five
3.18(0℃)
melting point
501℃
-15℃
boiling point
950℃
-
Solubility
Slightly soluble in cold water, soluble in hot water, insoluble in dilute hydrochloric acid, but soluble in concentrated hydrochloric acid and concentrated alkaline metal chloride solution, forming tetrachlorolead (II) anion complex ion.It is insoluble in alcohol and can form basic salt and double salt.
It can dissolve in concentrated hydrochloric acid to form hexachlorolead (Ⅳ) acid.Insoluble in concentrated sulfuric acid.
Preparation
It is usually prepared by reaction of lead monoxide or basic lead carbonate with hydrochloric acid, or by precipitation of lead nitrate with hydrochloric acid.
It is usually obtained by dissolving lead dioxide in cold concentrated hydrochloric acid or reacting concentrated sulfuric acid with ammonium hexachlorolead (Ⅳ) acid.[14]
purpose
It can be used for making pigment, solder or flux.[12]It is also used to produce various lead salts and lead pigments.
-
toxicity
The minimum lethal dose to rats is 2000mg/kg, and the lead entering the human body can be combined in the bones and hair, but only when concentrated in the liver.[13]
-
other
-
Stable only at low temperature[13]It decomposes at normal temperature (producing lead dichloride and chlorine), and it decomposes violently at 105 ℃ to explode.When encountering moisture and water, it is easy to hydrolyze to lead dioxide and hydrogen chloride, resulting in strong smoke.
Lead sulfate
also called
Lead alum
appearance
Usually white crystal or powder
molecular weight
three hundred and three point two six
relative density
six point two
decomposition temperature
Decomposition occurs at 1000 ℃
melting point
About 1170 ℃[15]
Solubility
Slightly soluble in water, insoluble in ethanol and dilute sulfuric acid, soluble in hot concentrated sulfuric acid, concentrated hydrochloric acid, concentrated nitric acid, concentrated lye, ammonium acetate, ammonium tartrate and other solutions.[15]
Preparation method and use
Lead sulfate is usually precipitated by the reaction of lead monoxide with sulfuric acid, or by the reaction of soluble lead salt solution with dilute sulfuric acid.It is often used as white pigment, raw material for making batteries and quick drying paint.[15]
application
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Lead is the raw material for making batteries, cables, bullets and ammunition, as well as an additive to gasoline.Lead compounds are used as raw materials for pigments, glass, plastics and rubber.Metal lead is widely used in manufacturing chemical and metallurgical equipment because of its excellent acid and alkali corrosion resistance.Lead alloys are used as bearings, movable type gold and solders.In addition, lead has also developed some new uses.For example, it can be used as a stabilizer of asphalt to extend the service life of pavement;High power battery pack for manufacturing shielding and nuclear waste storage tank of nuclear power plant, load adjustment of power sector, andMagnetohydrodynamicsDevices, etc.[5]
A brief history of application
Lead is one of the metals extracted earlier by human beings. It was discovered and applied as early as 3000 BC.Small figures made of lead were used in Egypt during the pre imperial period (as early as 3000 BC). Mesopotamia had made small containers or hammered thin pieces of lead in Uru III (3000 BC). The earliest found in China was the lead block unearthed from Erlitou Site in Yanshi, Henan Province, which existed about 3500 to 4000 years ago.In the tombs of the Shang Dynasty and the Western Zhou Dynasty, lead made jue, gu, zun, ding and ge were unearthed. The lead content of the lead ge in the Western Zhou Dynasty (11th century BC~771 BC) reached 99.75%.[8]It was not until the 15th century BC that lead was more commonly found in Palestine.However, it was not until the 17th and 18th centuries that lead began to be produced on a large scale. The main lead producing countries are the United States, the former Soviet Union, Japan, Germany, Britain, China, etc.[8]
Lead acid battery
Lead acid battery (hereinafter referred to as lead-acid battery) has a history of more than 150 years since its inception. Because of its low price, mature technology, reliable performance and other advantages, it has become the secondary battery with the largest output and the most widely used in the current chemical power supply, and has been widely used in various occasions of social production and life for a long time.[16]
The lead-acid battery is charged and discharged by using the solid state reaction of different valence states of lead. When the battery discharges, the active substances of the two electrodes become PbSO respectivelyfour, when charging, reaction directionReverse reaction directionThe electrolyte sulfuric acid is an active substance.The positive and negative electrode reactions are applicable to the dissolution precipitation mechanism rather than the solid ion transport or membrane formation mechanism.The standard cell voltage of lead-acid battery in the greenhouse is 2.1V.[16]
Cable sheath
The sheath materials are mainly chemical lead, lead alloy containing 1% antimony or arsenic, and lead alloy containing 0.03% calcium or hooves. Lead is used as the cable sheath for moisture-proof, anti-corrosion and shielding support.The lead used in the cable industry is mainly power cables and communication cables. Although most of the lead sheaths of domestic power communication cables have been replaced by plastics and other materials, a small number of cables still use lead sheaths.Due to the consideration of environmental protection, there are many disputes about the use of lead in the offshore submarine cable sheath abroad, but the lead consumption in this field still accounts for a large part of its use.[17]
chemical products
At present, there are quite a few lead compounds used in chemical industry.Only a few widely used products are introduced here.Lead oxide is widely used in paste mixtures of lead-acid battery grids, cement, glass, ceramics, and in the preparation of other lead compounds;Red lead is an important anti rust paint, which is used as primer and interior paint to prevent steel corrosion.
The important white anti-corrosive pigments in industry are lead carbonate monobasic, lead phosphite dibasic, lead phosphosilicate dibasic and lead silicate monobasic.Lead borate can be used in glass manufacturingFire retardant coatingPaint drier;Lead nitrate is used for pharmaceutical and ore flotation.In addition, lead chemical products are also used in electronic powder materials and color electronic ultrablack picture tubesLuminescent material。[17]
solder
Lead alloy solder is commonly referred to as soft solder, in whichTerne metalSolder is the most widely used and has a long history in all welding materials.It has a low melting point and can be used to connect most metals with simple heating methods without damaging the thermal sensitive elements.
For the application of traditional alloy solder, the manufacturer should pay special attention to the use of alloys with different tin content for specific welding objects and requirements.To achieve the purpose of saving expensive tin and reducing costs on the premise of meeting the use requirements.For example, solder with tin content not less than 5% is mainly used for sealing. It is often used to seal containers after pre surfacing, coat and weld metal, and can also be used for service temperature exceeding 120 ℃.[17]
Lead material
(1) Lead plate
Generally, the lead material is rolled to a width of less than 3.6m, a thin lead plate of any thickness, and a weight of 0.4mm thick lead plate.As a structural material, lead plate is an important corrosion resistant material in chemistry and related industries, which mainly benefits from the corrosion resistance of lead to a variety of corrosive environments.Of course, it can also be used as building structural materials, such as roof anti-corrosion board, bathroom floor.When the lead plate contacts with cement, it is generally coated with a layer of asphalt on the surface.AsX-rayAndGamma rayThe shielding layer is a familiar application.With the excellent shock absorption and sound insulation performance of lead, a large number of lead plates are also used in shock absorption and sound insulation.For example, steel and lead sheet damping pads installed under the building foundation to prevent vibration transmission;Pure lead can absorb most of the vibration energy released during an earthquake. This shock absorber was tested in an earthquake in Japan in recent years.[17]
(2) Lead pipe
Lead pipe in lead material is also a main aspect, which is widely used in chemical industry and drainage pipeline.The seamless tube is extruded with chemical lead or lead containing 6% antimony.Almost all kinds of pipes with diameters ranging from thin pipes to 300mm or larger have production applications.
(3) Wire mesh lead material
In the lead materials for construction, in addition to the use of lead plate, pipe, solder, there is also lead mesh for plugging;A considerable part of the above lead tin solders, as low melting point fusible alloys (alloys of lead and tin, bismuth, cadmium, indium, etc.), are almost all wire materials.The lowest melting point of the latter is below 100 ℃, which is used for automatic arc extinguishing, electric fuse, boiler plug, etc.
In developed countries, lead has become an independent consumption destination, especially in Britain, where lead skin is used as roof material to prevent radiation from atmosphere atoms.However, the production of lead materials in China is very small, with an annual output of about 10000 tons.With the improvement of people's life, lead material may become one of the main consumption uses of lead.[17]
Lead casting materials
The main casting materials of lead areBearing alloyAnd type alloy;The casting products include bearings, type plates, counterweights, sealing washers, warheads, ballast counterweights, and even the integral castings of the radiation shielding layer of large nuclear power plants.[17]
Lead composite
The lead sheet is sandwiched between two tin sheets and rolled into a tightly bonded Sn Pb Sn composite foil 0.01mm thick or thinner, which is commonly referred to as "lead foil".It is used for moisture-proof in the construction industry, or as the anti oxidation foil of grape and champagne bottles.Some are also used in the electronics industry.This "lead foil" is produced in large quantities abroad and widely used.However, there are gaps in both production and application in China.Of course, the more common and widely used lead composite is made by combining lead with stronger materials, and its performance is better than that of single two materials.Lead may be compounded with steel, concrete, wood, brick or other suitable materialsStructural compositesIt has excellent corrosion resistance and high strength.Although the strength of lead plastic composite is slightly lower, the composite material has excellent sound insulation performance.
Composite structures made by combining lead with stronger hard materials include:
① Basic lead composite structure: cast or extruded lead or lead alloy, on a limited composite base.Such as antimony containing lead valves, pumps, anodes and containers made by casting.
② Lead compound on high strength base: sheet, tubular or other extruded lead and its alloy, which are firmly combined with steel, wood, concrete, copper or other metals, and used as heating pipes, conveyors, floors, cable sheaths, roofs and anode plates.
③ Paste composite lead materials: sheets, tubes or other forms of lead and its alloys, which are connected with steel, concrete, wood or other materials with adhesive, and used as lead skin acid storage containers.
④ Metallurgical bonded lead composite material: heavy lead or lead alloy composite material metallurgically combined with steel, copper or other metals, used as a steel reaction pool for lead coating, and a lead coated copper cooling and heating coil.
⑤Inorganic materialsComposite lead: lead sheet is embedded between concrete or steel and ceramic tile materials, and the lead sheet is mechanically or chemically connected with the inner and outer layers.For example, cushion materials are embedded between the steel sheet and the inner layer for sulfuric acid mist washing, precipitation, collection, storage, etc.
⑥ Lead coated composite material: the coating is mechanically or metallurgically connected with the equipment surface, and has corrosion resistance.Apply Pb Sn on steel for roof, sink and chute.The above six lead composites all have the advantages of low material cost, low installation and maintenance cost, excellent corrosion resistance, long service life, and suitability for various operating conditions.[17]
Industry development
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Lead metal market
China's refined lead production from 2001 to 2014
China is rich in lead ore resources. With the increase of domestic demand for lead, the amount of lead ore mined in China has reached the first in the world.However, the concentration of China's lead smelting industry is relatively low. The total output of the top ten lead enterprises in China is less than 50% of that of the whole country, and 65% of the lead battery capacity is in the hands of several major producers in Zhejiang. The relative concentration of consumption makes the voice firmly in the hands of the buyer. Therefore, the buyer's market is an important feature of the domestic lead market.[18]
According to the data released by the National Bureau of Statistics, China's refined lead production in 2014 totaled 4.22 million tons, down 5.5% year on year.The output of refined lead in China from 2001 to 2014 is shown in the right figure:
Lead concentrate output in China from 2008 to 2014
Data also shows that in 2014, China's total production of lead concentrates reached 2.997 million tons, down 4.84% year on year.During 2010-2014, the growth rate of China's lead concentrate production declined year by year.The lead concentrate output in 2008-2014 is shown in the right figure:
Lead is one of the most important basic metals in the national economy, which is widely used in battery, cable sheath, automobile manufacturing, military industry and other industries.Lead acid battery is the main consumption area of lead, and the lead consumption accounts for more than 80% of the total lead demand.With the rapid development of the national economy, the social demand for industrial raw materials is increasing. Driven by the strong demand of the lead-acid battery industry, China's lead consumption has overtaken that of the United States, ranking first in the world.[18]
Lead industry distribution
The production layout of China's lead and zinc industry, based on the distribution of lead and zinc ore producing areas and construction conditions, has formed five production bases supporting lead and zinc mining, dressing, metallurgy and processing in Northeast China, Hunan, Guangdong, Guangxi, Yunnan, Sichuan and Northwest China after more than 40 years of development and construction. Its lead output accounts for more than 85% of the national total output, and zinc output accounts for 95% of the national total output.[19]
(1) Northeast production base
Northeast China is one of the earliest lead and zinc production bases in China.As early as the early 1950s, its lead production accounted for more than 80% of the national lead production, and played an important role in China's lead and zinc production.The Northeast Base is dominated by seven mines and two factories, namely, Qingchengzi Lead Zinc Mine, Bajiazi Lead Zinc Mine, Chaihe Lead Zinc Mine (pit closed now), Huanren Copper Zinc Mine, Hongtoushan Copper Zinc Mine, Xilin Lead Zinc Mine (pit closed now), Tianbaoshan Lead Zinc Mine, Shenyang Smelter, Huludao Zinc Plant.Seven mines and two factories are not onlyNortheast Lead and Zinc Production BaseOur pillar factories and mines are also the bases for cultivating scientific and technological talents.In the 1960s and 1970s, he sent a large number of experienced scientific and technological personnel, management personnel and production technicians to newly built lead-zinc enterprises across the country, making positive contributions to the development of China's lead-zinc industry.[19]
(2) Hunan Production Base
Hunan is rich in lead and zinc mineral resources, most of which can be developed and utilized.The lead-zinc plant and mine in the base was built in the 1950s and 1960s. The Hunan lead-zinc production base composed of Shuikoushan Mining Bureau, Taolin lead-zinc mine, Huangshaping lead-zinc mine, Dongpo lead-zinc mine and Zhuzhou Smelter was the largest lead-zinc production base for self-produced raw materials in the country at that time, and played an important role in the national output.[19]
(3) Production base in Guangdong and Guangxi
Guangdong and Guangxi are rich in lead and zinc resources. The two provinces are one of the large-scale lead and zinc production bases in China formed in the 1970s.Guangdong is dominated by Fankou Lead Zinc Mine and Shaoguan Smelter, followed by Bingcun Lead Zinc Mine, Changhua Lead Zinc Mine and Dajianshan Lead Zinc Mine.Guangxi has Siding Lead Zinc Mine, Daxin Lead Zinc Mine, Hesan Lead Zinc Mine, Liuzhou Zinc Products Factory and Dachang Mining Bureau.[19]
(4) Yunnan Sichuan production base
Yunnan is rich in lead and zinc mineral resources, and the current reserves of lead and zinc rank first in the country.The base's lead and zinc enterprises were also built in the 1950s and 1960s, mainly including Huize Lead and Zinc Mine, Lancang Laochang Lead and Zinc Mine, Kunming Smelter and Gejiujijie Smelter.Yunnan's lead and zinc mineral resources have broad prospects for development. In the 1990s, Jinding Mine of super large lead and zinc deposits was built.Sichuan has two major mines, Huidong Lead Zinc Mine and Huili Lead Zinc Mine, as well as a number of small and medium-sized mines, and the output of lead and zinc concentrates has soared.[19]
(5) Northwest production base
Northwest China is also rich in lead and zinc mineral resources, which are mainly distributed in Gansu, Shaanxi and Qinghai provinces. Moreover, the explored reserves of the western metallogenic belt have increased significantly, and the resource prospect is very considerable.The production of lead and zinc in this base is dominated by Baiyin Nonferrous Metals Company, including Baiyin Xiaotieshan Lead Zinc Mine, the Third Smelter and Northwest Lead Zinc Smelter, Shaanxi Qiandongshan Lead Zinc Mine, Erlihe Lead Zinc Mine, Yindongliang Lead Zinc Mine and Qinghai Xitieshan Mining Bureau.The production of lead and zinc in northwest China is less, but the development prospect is considerable.First, there are rich lead-zinc mineral resources. Located in the Xicheng Fengtai ore belt at the junction of Gansu and Shaanxi, more than 10 large and medium-sized lead-zinc silver gold deposits have been explored, of which Changba Lijiagou lead-zinc deposits reach a super large scale and silver deposits reach a large scale.Second, Changba is working hard to build a large mine, which will become the main mineral raw material supply base for the northwest smelter and one of the large lead and zinc mines in China.
In addition to the above five major lead and zinc production bases, a number of small and medium-sized mines have also been built in Inner Mongolia, Jiangxi, Guizhou and other provinces and regions.Among them, Wutonghua Lead Zinc Mine, Baiyinnuo Lead Zinc Mine, Ongniud Banner Dongzi Lead Zinc Mine and other mines in Inner Mongolia.Inner Mongolia is one of the main provinces and regions producing lead and zinc concentrates in China, with a great development prospect.Jiangxi has Yinshan Lead Zinc Mine, etc.Guizhou has Hezhang Lead Zinc Mine, Shanshulin Lead Zinc Mine, etc.[19]
Harm to human body
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Lead is one of the three major heavy metal pollutants, which is a serious hazard to human healthHeavy metal elementsThe ideal lead content in human body is zero.The human body mostly brings lead into the human body by ingesting food, drinking tap water, etc. 90% of the lead entering the human body is stored in the skeleton, and 10% is distributed to various tissues and organs of the whole body along with the flow of blood circulation, affecting red blood cells, brain, kidneyNervous system functionEspecially after infants absorb lead, more than 30% will remain in the body, affecting the growth and intellectual development of infants.[20]
As lead is cumulative poisoning, only when the lead content in the human body reaches a certain level can it cause physical discomfort. After long-term ingestion of lead, it will cause serious damage to the blood system and nervous system of the body, especially the harm to children's health and intelligence.[20]
In industrial production, lead is inhaled into the human body in the form of lead dust (smoke). Occupational lead poisoning is mostly chronic poisoning, and there are clinical symptoms of nervous, digestive, blood and other systems.The nervous system is mainly manifested asNeurasthenia、Multiple neuropathyAnd encephalopathy.Neurasthenia is one of the early and common symptoms of lead poisoning, which is manifested as dizziness, headache, general weakness, memory loss, sleep disorder, dreaminess, etc.Multiple neuropathy can be divided into sensory type, motor type and mixed type:[21]
Sensory type: numbness of extremities and glove sock type of extremitiesSensory disturbance；Athletic manifestations include muscle weakness and muscle paralysis.Lead poisoning encephalopathy is rarely seen. It is the most serious lead poisoning, which is characterized by headache, nausea, vomiting, high fever, irritability, convulsions, lethargy, mental disorder, coma and other symptoms.Mild symptoms of digestive system can be manifested as metallic taste in the mouth, loss of appetite, abdominal distension, discomfort, abdominal pain and constipation;Abdominal colic occurs in severe cases.The blood system is mainly interfered by leadhemoglobinSynthesis process, which leads to anemia.Generally, lead poisoning can recover quickly after lead elimination treatment. Except for lead poisoning encephalopathy, there are few sequelae.[21]
lead pollution
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Source of pollution
(1) Direct pollution
When it comes to food production process and food containers, direct contact with lead in the production process of food or direct addition of lead containing raw materials due to production process will lead to lead pollution. Now it is more common to produce lead containing canned food, preserved eggs, popcorn and other foods.[20]
The lead exceeding rate of 2766 food samples in 16 categories monitored from 2001 to 2008 was 5.42%. Although the overall pollution was not serious, the lead content in preserved eggs and other foods was high;The detection of lead and cadmium pollution in food in Guangdong Province from 2009 to 2010 showed that kelp, laver and preserved eggs were the main lead contaminated foods, with the exceeding standard rates of 20%, 30% and 28% respectively;In addition, the survey shows that children who do not often eat canned food, preserved eggs, popcorn, etc. have high IQ. These survey results show that the harm of food directly contaminated with lead cannot be underestimated.[20]
(2) Indirect pollution
Food raw materials cause lead pollution through soil, air, water and other channels during the growth and production process.With the development of modern industry and the discharge of industrial "three wastes", toxic heavy metal lead can enter the ecosystem through various ways.Data shows that as early as 1997, the area of lead pollution in China has reached 20 million meterstwo, accounting for 20% of the total cultivated land area in China. With the aggravation of pollution in recent years, the pollution area has exceeded the pollution area in 1997;At the same time, there are reports of heavy metal lead pollution through soil, air, water, etc. The blood lead incident in Zhongshan City, Guangzhou in May 2011 was the result of water pollution.[20]
Control method
(1) Contain the source of pollution
China is a large country of lead production, and now China's lead production has ranked first in the world. Therefore, if the lead ore is not properly controlled in the production process, it is very easy to have a large-scale lead pollution event. The lead poisoning event in Fengxiang, Shaanxi Province in early 2012 was caused by the failure to move the nearby residents in time before mining, leading to the lead ore mining pollution event.[20]
(2) Control circulation channels
The transmission channels include polluting food by means of water source, tableware, cans, etc., regularly detecting the level of lead content in the water in the threatened area, strictly preventing heavy metal lead from entering food through normal circulation channels, in addition, regularly monitoring the lead content of food on the market at random, and timely handling food found to exceed the standard.[20]
(3) Treatment of victims
Lead does great harm to human body. When the lead content in children's body reaches about 10 μ g/dL, their intelligence will be 9% lower than that of children of the same age. It is one of the problems that must be considered at present to regularly monitor the blood lead of people in threatened areas and treat poisoning patients in time.[20]
