How is asphalt extracted?

Asphalt materials are divided into two categories. The first category is asphalt, mainly natural asphalt and petroleum asphalt. The second category is tar pitch, which mainly includes coal pitch, shale pitch, peat pitch and wood tar. There are two kinds of natural asphalt refining, one is direct mining, such as refining asphalt from asphalt lake in Trinidad and Tobago; Second, it is extracted from sandstone and sand. Petroleum asphalt is made of petroleum products and can be classified according to the following systems:

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.

manufacturing 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, knocking 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.

The second category is tar pitch, which is rarely used now, so I won't talk about it for the time being. Description: Petroleum asphalt information comes from Tianya Q&A.