English name: asphalt
English Name 2: Asphalt
Physical and chemical characteristics
Extract: Coal and petroleum.
Main ingredients:
Content: 99.48%.
Appearance and properties: black liquid, semi-solid or solid.
Boiling point (℃): < 470
Relative density (water =1):1.15-1.25.
Flash point (℃): 204.4
Ignition temperature (℃): 485℃
Lower explosive limit% (volume ratio): 30 (g/cm3)
Solubility: insoluble in water, acetone, ether and dilute ethanol, soluble in carbon disulfide and carbon tetrachloride. Molten sodium hydroxide
Main uses: used in coatings, plastics, rubber and other industries and paving roads.
Health hazards: asphalt and its smoke are irritating to skin and mucosa, and have phototoxicity and tumorigenic effects. The toxicity of three main asphalts in China: coal tar asphalt > shale asphalt > petroleum asphalt, and the first two are carcinogenic. The main skin damage of asphalt is: phototoxic dermatitis, and the skin damage is limited to exposed parts such as face and neck; Melanosis, skin lesions are often symmetrically distributed in the exposed parts, which are flaky, brown-dark brown-brown black; Occupational acne; Verrucous vegetation and thermal burns caused by accidents. In addition, there are general symptoms such as dizziness, head swelling, headache, chest tightness, fatigue, nausea, loss of appetite, eye, nose and pharynx irritation.
Environmental hazard: it is harmful to the environment and can pollute the atmosphere.
Danger of explosion: This product is flammable and irritating.
Hazard characteristics: flammable in case of open fire and high heat. Toxic and irritating smoke is emitted when burning.
Removal: If the clothes are accidentally stained with asphalt, try washing them with sodium hydroxide. ..
Asphalt classification
Asphalt is mainly divided into three types: coal tar asphalt, petroleum asphalt and natural asphalt;
1. Coal tar pitch: Coal tar pitch is a by-product of coking, that is, the black substance left in the distiller after tar distillation. It is just different from refined tar in physical properties, and there is no obvious boundary. The general classification method is to specify that the softening point below 26.7℃ (vertical method) is tar and the softening point above 26.7℃ is asphalt. Coal tar pitch mainly contains anthracene, phenanthrene and pyrene which are difficult to volatilize. These substances are toxic, and the properties of coal tar pitch are different due to the different contents of these components. The change of temperature has a great influence on coal tar pitch, which is easy to crack in winter and soften in summer. It has a special smell when heated; After heating to 260℃ for 5 hours, anthracene, phenanthrene, pyrene and other components contained in it will volatilize.
2. Petroleum asphalt: Petroleum asphalt is the residue after crude oil distillation. Depending on the degree of refining, it will become liquid, semi-solid or solid at room temperature. Petroleum asphalt is black and shiny, and has high temperature sensitivity. Because it has been distilled to more than 400℃ in the production process, it contains few volatile components, but there may still be high molecular hydrocarbons that have not volatilized, which is more or less harmful to human health.
3. Natural asphalt: Natural asphalt is stored underground, and part of it forms a seam or accumulates on the surface of the earth's crust. Most of this asphalt has undergone natural evaporation and oxidation, and generally does not contain any toxins.
Asphalt materials are divided into two categories: asphalt and tar asphalt. Asphalt is divided into natural asphalt and petroleum asphalt. Natural asphalt is the residue of oil seeping out of the surface after long-term exposure and evaporation. Petroleum asphalt is a product obtained by treating the residual oil in refined petroleum with appropriate technology. Tar asphalt is a reprocessed product of tar, which is obtained by dry distillation of organic matter such as coal and wood. The asphalt used in engineering is mostly petroleum asphalt, which is a mixture of complex hydrocarbons and their nonmetallic derivatives. Usually, the flash point of asphalt is between 240℃ and 330℃, and the ignition point is about 3℃~6℃ higher than the flash point. The construction temperature should be controlled below the flash point.
★ Hazard★:
Asphalt is a brownish-black organic gelling substance, including natural asphalt, petroleum asphalt, shale asphalt and coal tar asphalt. The main components are asphaltene and gum, followed by high-boiling mineral oil and a small amount of compounds of oxygen, sulfur and chlorine. Glossy, liquid, semi-solid or solid, brittle at low temperature, good adhesion and corrosion resistance.
Among the four kinds of asphalt, coal tar asphalt is the most harmful. A large amount of asphalt smoke is emitted during the production of electrode roaster. Because asphalt contains fluorescent substances, the carcinogen 3.4 benzopyrene is as high as 2.5%-3.5%, which volatilizes with flue gas when it is treated at high temperature. Asphalt flue gas is yellow gas, in which tar particles are fine. The content of 3,4 benzopyrene in asphalt flue gas discharged from electrode roaster is 1.3-2 mg/m3.
Asphalt dust can cause poisoning through the respiratory tract, pollute the skin, and lead to dermatitis, blurred vision, conjunctivitis, chest tightness, abdominal diseases, palpitations, headaches and other symptoms. It has been proved by scientific experiments that 3,4 benzopyrene contained in asphalt and asphalt smoke is one of the main causes of skin cancer, lung cancer, gastric cancer and esophageal cancer.
Living in air polluted by asphalt is easy to reduce immunity.
Phenols, compounds, anthracene, naphthalene, pyridine, etc. , which is the main component of asphalt and its flue gas, is irritating to skin and mucosa, and is coated with 30%.
Coal tar pitch coated with toluene solution for three times showed hyperkeratosis and cracking after local inflammation.
Asphalt, anthracene, phenanthrene and pyridine are all phototoxic substances, which will cause photobiological effects under the action of ultraviolet rays. Asphalt induced light
Chemical reaction refers to the photochemical reaction of asphalt under the action of light energy under aerobic conditions, which generates free radicals and peroxides.
Compounds cause cell damage, so they are non-immune diseases.
Animals breed asphalt cancer. In China, asphalt can also cause skin cancer in mice skin coating experiments. Most of them are phospholipid epithelial carcinoma, and a few are keratocarcinoma.
Mastoid tumor It is generally believed that kerosene asphalt is the most carcinogenic, natural asphalt is not carcinogenic, but it is carcinogenic to petroleum asphalt.
There is no agreement yet.
The effect of coal tar pitch coating on animal weight gain is more obvious than that of petroleum pitch, and the skin coating of coal tar pitch is more attractive than its smoke.
It is harmful to animals. It is suggested that coal tar pitch has a certain systemic effect on animals, and its degree of action and absorption route are as follows
Close.
clinical
6. 1 skin damage
6. 1. 1 Phototoxic dermatitis This disease often occurs after exposure to asphalt dust or smoke and sunlight. Arrive in a few minutes after exposure.
1-2 days (mostly several hours) can cause disease. Skin lesions are limited to exposed parts such as face and back of neck, especially eyelids and cheekbones.
Write it. The skin lesions are sunburn, showing well-defined red and bright red spots, often accompanied by edema, blisters, blisters, and even bullae in severe cases.
Erosion and seepage. Skin lesions reached the peak within 1-2 days, generally stopped contact for 3-5 days and quickly subsided, with slight chaff-like scales attached locally.
Fragments, often secondary to temporary mild pigmentation. Consciously burning pain, individual mild itching.
6. 1.2 Melanosis is very common. The disease is often symmetrically distributed in the exposed parts of the face and neck, and the forearm is also involved. It's especially good for the eyes.
Circumferential, temporal, forehead hairline and internal angle, followed by nose, cheeks and mouth. Skin lesions are mostly flaky, dark and brown-black.
Brown and black, sometimes reddish brown or lavender. It varies in size and shape, and its edges are mostly blurred. Forearm pigmentation
Often centered on pores, the affected pores are slightly keratinized; Sometimes light brown and grayish purple pigmentation spots alternate with normal skin and mix together.
In a fog.
There is often a history of recurrent episodes of asphalt phototoxic dermatitis, often accompanied by asphalt acne.
This disease is a chronic process. Every sunshine will make the disease worse. Disengagement and desire for improvement lead to recovery.
6. 1.3 acne
Occupational acne caused by asphalt is mainly manifested in the inflammatory diagnosis of blackhead acne, broken hair and folliculitis. This disease is easy to come into direct contact with.
Face, finger back, back of hand, forearm and other parts often affect the parts of clothes and trousers contaminated by asphalt, such as thigh extension, and even.
There is hair in the trunk. Blackhead acne is a black spot with large pores, and there are often small white induration below. Blackheads caused by asphalt are generally
It is thicker than that caused by chloride, and its distribution is scattered, mainly in the face, especially in the temporal, eyebrow, nose and eyes.
Eyelids and auricles will also be affected. Follicular inflammatory red papules are follicular papules with yellow-white pustules at the top, which can develop into severe cases.
Furuncle and induration can leave scars; Often scattered on the face and forearm. Hair breaks and thickens, and local pores often expand.
There is slight keratinization, mainly distributed on the dorsal surface of the first finger and the radial extension surface of the forearm. The onset of this disease is not limited by age. Lack of conscious symptoms
For example, sometimes dryness, folliculitis and furuncle are very painful.
6. 1.4 verrucous vegetation
It occurs on the back of hand, wrist and face, and can also spread to scrotum. Similar to verruca plana, the surface is light brown and flat.
Papule, needle cap or mung bean size, round or irregular, rough or smooth surface, clear boundary. Scattered or densely distributed.
No symptoms or slight itching. Generally, the longer the length of service, the higher the incidence rate and the more skin lesions. Verrucous vegetation can fade naturally, or it can
Will develop into epithelioma.
6. 1.5 thermal burn
It is mostly caused by accidents such as splashing water and slipping. Hot liquid asphalt can cause thermal burns to the skin. Clinical manifestations and systemic thermal burns
Similarly, only the affected skin surface is covered with black asphalt, which adheres tightly to the wound surface and is difficult to remove.
6.2 Symptoms of eyes, nose and pharynx
The damage of asphalt dust and smoke to eyes is mainly pharyngolaryngitis, sometimes accompanied by superficial punctate keratitis, and long-term workers have wings
Pterygium accounts for a certain proportion. The nasopharynx is often dry and burning, which can also cause rhinitis and pharyngitis.
6.3 Systemic symptoms
After smelling asphalt, dizziness, head swelling, headache, chest tightness, fatigue, nausea or cough, palpitation, tinnitus and so on may occur.
Suitable, especially when working in the hot sun. Symptoms of separation (such as after work) are often relieved quickly. In severe cases (such as severe phototoxicity)
Dermatitis can be accompanied by fever.
Oil asphalt
1. Definition
English name: petroleum asphalt
Petroleum asphalt is the product of crude oil processing, which is black or dark brown viscous liquid, semi-solid or solid at room temperature. It mainly contains hydrocarbon and non-hydrocarbon derivatives soluble in trichloroethylene, and its properties and composition vary with crude oil sources and production methods.
2. Product performance
Petroleum asphalt is the residue after crude oil distillation. Depending on the degree of refining, it will become liquid, semi-solid or solid at room temperature. Petroleum asphalt is black and shiny, and has high temperature sensitivity.
Petroleum asphalt can be classified according to the following system:
According to the production method, it can be divided into straight-run asphalt, solvent deoiled asphalt, oxidized asphalt, mixed asphalt, emulsified asphalt and modified asphalt.
According to the appearance, it is divided into: liquid asphalt, solid asphalt, diluent, emulsion, modified body and so on.
According to the use, it is divided into: road asphalt, building asphalt, waterproof and moisture-proof asphalt, and various special asphalt named after the use or function.
3. Production method
(1) distillation method: crude oil is distilled at normal pressure to separate out light fractions such as gasoline, kerosene and diesel oil, and then vacuum distillate oil (residual pressure 10~ 100mmHg) is separated by vacuum distillation. When the residual residue meets the specifications of road asphalt, asphalt products can be directly produced. The obtained asphalt, also called straight-run asphalt, is the main method to produce road asphalt.
(2) Solvent precipitation method: nonpolar low-molecular-weight alkane solvents have different solubility for each component in vacuum residue. By using the solubility difference, each component can be separated, so that the components that are unfavorable to asphalt properties can be removed from vacuum residue to produce asphalt products that meet the specifications. This is the solvent precipitation method.
(3) Oxidation method: At a certain range of high temperature, air is blown into vacuum residue or deoiled asphalt to change its composition and performance, and the obtained product is called oxidized asphalt. Under the action of high temperature and blowing, vacuum residue will vaporize, and a series of reactions such as dehydrogenation, oxidation, polymerization and condensation will occur at the same time. This is a very complex multi-component interaction comprehensive reaction process, which is not only an oxidation reaction, but also known as oxidation method and oxidized asphalt, air blowing method and air blowing asphalt.
(4) Blending method: Blending method refers to blending the four components of asphalt composed of the same crude oil again according to the proportion required by quality requirements, and the obtained product is called synthetic asphalt or recycled asphalt. With the development of technology, the sources of blending components have been expanded. For example, the residues or components of the same crude oil or different crude oils after primary and secondary processing with various industrial waste oils can be used as blending components, which reduces the dependence of asphalt production on oil source selection. With the increasing shortage of crude oil suitable for asphalt production, the flexibility and economy of blending methods have been paid more and more attention and widely used.
(5) Emulsification method: The surface tension of asphalt and water is very different, and they will not be mutually soluble at room temperature or high temperature. However, when asphalt is subjected to high-speed centrifugation, shearing, mashing and other mechanical actions, it becomes particles with a particle size of 0. 1~5 microns and is dispersed in the water medium containing surfactant (emulsifier-stabilizer). Because the emulsifier can be directionally adsorbed on the surface of asphalt particles, the interfacial tension between water and asphalt is reduced, and asphalt particles form a stable dispersion system in water, which is an oil-in-water emulsion. This dispersion system is brown, with asphalt as dispersed phase and water as continuous phase, and has good fluidity at room temperature. In a sense, emulsified asphalt is to "dilute" asphalt with water, thus improving the fluidity of asphalt.
(6) Modified asphalt: Many changes have taken place in modern highways and roads: the traffic flow and driving frequency have increased sharply, the axle load of freight cars has increased continuously, and one-way driving in separate lanes is widely implemented, which requires further improvement of the pavement's anti-fluidity, that is, the ability to resist rutting at high temperature; Improve flexibility and elasticity, that is, crack resistance at low temperature; Improve wear resistance and prolong service life. Long-span prestressed roof panels are widely used in modern buildings, which require that the roof waterproof material adapt to large displacement, be more resistant to harsh high and low temperature weather conditions, have good durability, be self-adhesive, be convenient for construction and reduce maintenance workload. These changes in the use environment pose a severe challenge to the performance of petroleum asphalt. In order to meet the above demanding requirements, people began to pay attention to the modification of petroleum asphalt. After decades of research and development, a wide variety of modified road asphalt, waterproofing membrane and coatings have appeared, showing certain practical engineering effects. However, in view of the fact that the price of modified materials is usually 2~7 times higher than that of ordinary petroleum asphalt, users have not fully grasped the engineering properties of materials, and the output of modified asphalt has grown slowly. At present, modified road asphalt is mainly used in airport runways, waterproof bridge decks, parking lots, sports fields, heavy traffic pavements, intersections, road bends and other special occasions. Recently, Europe has applied modified asphalt to the maintenance and reinforcement of road network, which has greatly promoted the wide application of modified road asphalt. Modified asphalt waterproofing membrane and coating are mainly used for waterproofing of high-grade buildings. With the progress of science and technology and the development of economic construction, the variety development and production technology of modified asphalt will be further promoted. The variety and preparation technology of modified asphalt depend on the type and dosage of modifier and the composition and performance of matrix asphalt (original asphalt). Because there are many kinds and shapes of modifiers, in order to form a uniform material for engineering application with petroleum asphalt, various types of modifiers have been evaluated for many years, and corresponding formulas and preparation methods have been developed, but most of the modified asphalt that has been applied to engineering at present belongs to patented technology and patented products.
4. Main uses
It is mainly used as infrastructure materials, raw materials and fuel, and its application scope is such as transportation (roads, railways, aviation, etc. ), construction, agriculture, hydraulic engineering, industry (extractive industry, manufacturing), civil engineering and other departments.
5. Packaging and storage
Asphalt may need to be stored in storage tanks during production and use. If handled properly, asphalt can be heated repeatedly and kept at a high temperature for a long time without seriously damaging its performance. However, if exposed to oxygen, light and overheating, the asphalt will become hard. The most obvious sign is that the softening point of asphalt increases, the penetration decreases and the ductility becomes worse, which makes the performance of asphalt lose. [Edit this paragraph] Petroleum-based colored asphalt Petroleum-based colored asphalt series has the characteristics of bright and fine color, excellent adhesion, excellent resilience and good resilience, which can meet the technical requirements of colored asphalt pavement under different climatic conditions. Because of its rich color selection, excellent physical and chemical properties and road performance, it can be widely used in parks, squares, playgrounds and landscape areas to beautify the environment and show natural interest; It can also be used in intersections, crosswalks and accident-prone areas, which is convenient for operation and management, maintains traffic safety and has both aesthetic and practical effects.
Its product performance and characteristics: good high-temperature stability, low-temperature crack resistance, water damage resistance and durability, excellent adhesion and high elastic recovery rate. But also has excellent cost performance, bright color, durability, convenient maintenance and health.
Usage: Generally, the mixing temperature shall not exceed 180℃, and the mixed stone with similar or light color to petroleum-based colored asphalt shall be selected, and the paving equipment shall be clean during mixing. Other construction methods are the same as heavy traffic road asphalt. [Edit this paragraph] The development status of China's asphalt industry In 2008, the total output of asphalt in China was about 8.48 million tons, a year-on-year decrease of 880,000 tons or 9.4%. Among them, the total output of China Petroleum and China Petrochemical Group is about 4.9 million tons, down 3% year-on-year, accounting for 57.8% of the total asphalt output in China; The output of local refineries is about 20 1 10,000 tons, down 25.4% year-on-year, accounting for 23.7% of the total output.
The main reasons for the sharp drop in asphalt output of local refineries in 2008 are as follows: on the one hand, due to the continuous increase in international crude oil prices in the first half of the year, the overall operating rate of local refineries is at a new low in recent years, and the asphalt output has decreased significantly year-on-year; On the other hand, although the international crude oil price began to fall from the high level in Shaanxi at the end of July, domestic economic growth slowed down due to the US financial crisis. In the second half of the year, the demand of asphalt market continued to be weak and the price continued to fall, which seriously hit the enthusiasm of local refineries to start producing asphalt. Overall, the operating rate of local refineries was at a low level, and the proportion of asphalt production decreased significantly year-on-year.