Dangerous goods are the general name of inflammable, explosive and strongly corrosive goods. The transportation of dangerous goods has great danger, and a little attention may cause material losses or casualties. Dangerous goods can be divided into the following types according to different nature.
According to the two national standards GB13690-2009 "Classification and Marking of Commonly Used Dangerous Chemicals" and GB6944-2005 "Classification and Designation of Dangerous Goods", chemicals are divided into 8 categories according to their risk: ① explosives ② compressed gas and liquefied gas ③ flammable liquid ④ flammable solid, spontaneous combustion articles and wet flammable articles ⑤ oxidant and organic peroxide ⑥ toxic and infectious articles ⑦ radioactive articles ⑧ corrosion.
Category 1 explosive
This type of chemical refers to the material that can have a violent chemical reaction under the action of the outside world (such as heat, pressure, impact, etc.), produce a large amount of gas and heat instantly, make the surrounding pressure rise rapidly, explode, and cause damage to the surrounding environment. It also includes no overall explosion risk, but with combustion, ejection and minor explosion risk. Or produce only heat, light, sound or smoke and other functions of one or several pyrotechnic articles.
Explosive is the principal characteristic of all explosives
All of these articles have chemical instability. Under the action of certain external factors, they will undergo violent chemical reactions, which mainly have the following four characteristics:
· Very fast chemical reaction. The chemical reaction is usually completed in 1/10,000 of the time, because the energy of the explosion is released in a very short time, so it has great destructive power.
· A lot of heat is generated during the explosion. This is a major source of explosives.
· Large amounts of gas are generated, resulting in high pressure. The resulting shock wave is very destructive to surrounding buildings.
It is very sensitive to impact, friction, temperature, etc
The explosion of any kind of explosive requires the outside world to supply it with a certain amount of energy - the detonation energy. The minimum initiation energy required for an explosive is the sensitivity of the explosive. Sensitivity is a very important indicator to determine the explosive risk of an explosive. The higher the sensitivity, the greater the explosive risk.
Some of the explosives are also somewhat toxic
For example, TNT, nitroglycerin, mercury and so on all have certain toxicity.
Reacts with acids, bases, salts and metals
Some explosives react with certain chemicals, such as acids, bases, and salts. The resulting products are more explosive chemicals. For example, picric acid can react with some carbonates to form more explosive picrates; Picric acid is struck by copper, iron and other metals and immediately explodes.
Class 2 compressed and liquefied gases
A chemical strain of this class means a gas dissolved under compression, liquefaction or pressure and in one of two ways:
When the critical temperature is below 50 ° C, or at 50 ° C, the vapor pressure is greater than 294KPa of compressed or liquefied gas;
When the temperature is 21.1℃, the absolute pressure of the gas is greater than 275KPa, or at 54.4℃, the absolute pressure of the gas is greater than 715KPa compressed gas. Or at 37.8℃, Reid vapor pressure greater than 275KPa liquefied gas or pressure dissolved gas.
Item 1 Flammable gas
Such gases are highly combustible and can form explosive mixtures when mixed with air. At normal temperature and pressure in the open fire, high temperature will occur combustion or explosion. Or poisoning
All compressed gases are hazardous, because they are under high pressure, some gases have inflammable, explosive, combustive, highly toxic and other properties, in the case of heat, impact, easy to cause combustion explosion or poisoning accidents.
The second term is non-flammable gas
Non-gas system refers to non-toxic, non-flammable gases, including combustion supporting gases. But high concentration can asphyxiate. Combustion-supporting gas has a strong oxidation effect and can be burned or exploded in the presence of grease.
Item 3 Toxic gases
This kind of gas is toxic, and the toxicity index is the same as that of class 6. It has strong toxic, suffocating, burning and stimulating effects on humans and animals. Some of them are also flammable, oxidation, corrosion and other properties.
Class 3 Flammable liquids
This class of chemical strains refers to flammable liquids, mixtures of liquids or liquids containing solid substances, but does not include liquids which have been included in other classes because of their danger. Its closed cup flash point is equal to or below 61℃.
According to the flash point is divided into the following three:
Item 1 low flash point liquid
Refers to the liquid whose flash point is lower than -18℃;
Flashpoint liquid in term 2
Refers to the liquid with the flash point of the closed cup at -18℃ to 23℃;
Item 3 high flash point liquid
Refers to closed cup flash point at 23℃ to 61℃ liquid.
Flammable liquids have the following characteristics:
High flammability
The main characteristic of flammable liquid is that it has a high degree of flammability, fire, heat and oxidant contact with the risk of combustion, the size of the risk and liquid flash point, spontaneous combustion point, the lower the flash point and spontaneous combustion point, the greater the risk of ignition.
Explosive property
Due to the low boiling point of flammable liquid, the vapor volatilization and air mix, the concentration is easy to reach the explosion limit, often explosion in the fire source.
Highly fluid diffusivity
The viscosity of flammable liquid is generally very small, not only itself easy to flow, but also because of infiltration, infiltration and capillary phenomenon, even if the container only very fine cracks, flammable liquid will leak out of the container wall. A leak easily evaporates, creating flammable vapors that are heavier than air and can accumulate in potholes, increasing the risk of combustion and explosion.
Charge accumulation
Some flammable liquids, such as benzene, toluene, gasoline, etc., have high resistivity and are easy to accumulate static electricity and generate static sparks, resulting in fire accidents.
Expansibility under heat
The expansion coefficient of flammable liquid is relatively large, after heating the volume is easy to expand, at the same time its vapor pressure also rises, so that the internal pressure in the sealed container increases, resulting in "drum", or even burst, when the container burst spark and cause combustion explosion. Therefore, flammable liquid should be stored away from heat; When filling, the container should leave a gap of more than 5%.
toxicity
Most flammable liquids and vapors have varying degrees of toxicity. Therefore, in the process of operation, we should do a good job of labor protection.
Flammability is the main characteristic of flammable liquid. Special attention should be paid to:
- No fireworks, away from fire, heat source;
- It is forbidden to use spark-prone iron tools and wear shoes with iron nails;
Class 4 Flammable solids, spontaneous combustibles and wet flammable articles
Item 1 Flammable solids This chemical class refers to solids that have a low ignition point, are sensitive to heat, impact and friction, are easily ignited by external ignition sources, burn rapidly and may emit toxic fumes or gases, but do not include substances listed as explosives.
(1) The main characteristics of flammable solids are easy to be oxidized, easy to decompose or sublimate when heated, and often cause strong and continuous combustion in the case of open fire.
(2) Contact with oxidants, acids, etc., the reaction is violent and combustion explosion occurs.
(3) It is also sensitive to friction, impact and vibration.
(4) Many flammable solids are toxic, or the products of combustion are toxic or corrosive.
For flammable solids should pay special attention to dust explosion!
Item 2 Spontaneous combustion articles
This chemical series refers to the low spontaneous combustion point, easy to occur in the air oxidation reaction, release heat, and self-combustion.
Combustibility is the main characteristic of spontaneous combustion
Spontaneous combustion materials have no regularity in chemical structure, so spontaneous combustion materials have different spontaneous combustion characteristics:
(1) Yellow phosphorus is lively, easy to oxidize, and the ignition point is particularly low, once exposed to air soon cause spontaneous combustion. But yellow phosphorus doesn't react with water, so it's usually stored in water. In addition, yellow phosphorus itself is extremely toxic, and the product of its combustion phosphorus pentoxide is also a toxic substance, which can generate highly toxic metaphosphate when it meets water. So in case of phosphorous combustion, attention should be paid to prevent poisoning in the process of rescue.
2) diethylzinc, triethyl aluminum and other organometallic compounds, not only in the air can spontaneous combustion, water will also be strongly decomposed, produce flammable hydrogen, causing combustion and explosion. Therefore, storage and transportation must be filled with inert gas or specific container packaging, fire can not be saved with water.
According to the different characteristics of spontaneous combustion articles to take corresponding measures!
Item 3 In case of wet flammable goods
This chemical series refers to some articles which, when exposed to water or damp, have a violent chemical reaction and give off a large amount of flammable gas and heat, can burn or explode without an open flame.
In addition to reacting with water, flammable substances can also react with acid or oxidizer when they encounter wet, and the reaction is more intense and more dangerous than that when they encounter water. Therefore, storage, transportation and use, pay attention to waterproof, moisture-proof, strictly prohibit fire close, and other properties of contradictory substances isolated storage.
In case of fire caused by wet flammable materials, it is strictly prohibited to use water, acid and alkali foam, chemical foam to fight the fire!
Class 5 oxidants and organic peroxides
Oxidizer number one
Oxidizer refers to the substance in high oxidation state, with strong oxidation, easy to decompose and give off oxygen and heat. Including organic matter containing peroxy, which is not necessarily inflammable by itself but can cause the combustion of combustibles; With soft powder can form explosive mixture, sensitive to heat, vibration or friction.
Oxidizer has a strong ability to obtain electrons, has a strong oxidation, acid and base, high temperature, vibration, friction, impact, moisture or with inflammable goods, reducing agents and other contact can quickly decompose, have the risk of combustion, explosion.
The second term is organic superoxidant
Organic peroxide refers to organic matter containing peroxy in its molecular composition, which is inflammable and explosive, easy to decompose, and extremely sensitive to heat, vibration and friction.
Class 6 toxic and infectious substances
Item 1 Poison
Specific indicators through the mouth: LD50≤500 mg/kg (solid)
LD50≤2000 mg/kg (liquid)
Percutaneous: LD50≤1000 mg/kg(24hr contact)
Inhalation: LC50≤10 mg/L (dust, smoke, vapor)
Item 2 Infectious material
This chemical class refers to substances that contain pathogenic microorganisms and can cause sickness and even death.
Class 7 radioactive articles
This class of chemical strains refers to articles with specific activity greater than 7.4×10Bq/kg.
radioactive
Radiation emitted by radioactive materials can be divided into four types: alpha rays, also known as alpha rays; Beta rays, also called alpha rays; Gamma rays, also known as gamma rays; And the neutron stream. All kinds of rays are harmful to the human body.
Many radioactive substances are highly toxic
They cannot be neutralized by chemical methods so that they do not emit radiation, and they can only be removed by means of either appropriate removal or absorption and shielding with appropriate materials.
Class 8 corrosive products
This class of chemicals refers to solids or liquids that can burn human tissue and cause damage to materials such as metals. Visible necrosis within 4 hours of contact with skin, or at 55℃, uniform annual corrosion of solid or liquid over 6.25 mm on the surface of No. 20 steel. This class of chemicals can be divided into three categories according to their chemical properties:
Item 1 Acid etch
The second alkaline etch
Item 3 Other corrosive products
Strong corrosion
In the chemical dangerous goods, corrosive goods are more active chemical properties, and many metals, organic compounds, animal and plant organism chemical reaction substances. This kind of substance can burn human tissue, metal, animal and plant organisms, fiber products have strong corrosion.
Most corrodes have varying degrees of toxicity, and some are even violent drugs.
flammability
Many organic corroded items are inflammable. Such as formic acid, glacial acetic acid, benzoyl chloride, acrylic acid, etc.
oxidability
Such as nitric acid, sulfuric acid, perchloric acid, bromine, and so on, when these items contact wood chips, sugar, gauze and other combustibles, oxidation reaction will occur, causing combustion.
As an essential item for economic development, dangerous goods need to exist. At the same time, due to its huge damage, it must be properly preserved, strictly observe the operation process, maintain high vigilance, strengthen monitoring, and prevent accidents.
