Femtosecond detection shows that fuel oil is mainly composed of petroleum pyrolysis residue and straight-run residue, which is characterized by high viscosity and contains many non-hydrocarbon compounds, resins and asphaltenes. 1 No.2 and No.2 are distillate fuel oils, which are suitable for domestic or industrial small burners. No.4 light fuel oil and No.4 fuel oil are heavy distillate fuel oil or fuel oil mixed by distillate fuel oil and residual oil. No.5 light, No.5 heavy, No.6 and No.7 are residual fuel oils with increasing viscosity and distillation range. For loading and unloading and normal atomization, it is generally necessary to preheat at low temperature. The most commonly used fuel oils in China are No.5 light, No.5 heavy, No.6 and No.7 fuel oils. In the new standard, the viscosity control and classification of No.5-7 fuel oils are classified according to the kinematic viscosity of 100℃, and imported fuel oils are basically classified according to the kinematic viscosity of 50℃, which is divided into two categories: kinematic viscosity of 50℃ ≥ 180mm/s and kinematic viscosity of 50℃ ≥ 380 mm/s.

Its physical and chemical properties mainly include:

stickiness

Viscosity is the most important performance index of fuel oil and the main basis for classifying fuel oil grades. This is an index to measure the liquidity impedance and its scale.

Represents the fluidity, pumpability and atomization performance of fuel. For high viscosity fuel oil, it is generally necessary to preheat to reduce the viscosity to a certain extent, and then enter the burner to facilitate spray atomization at the nozzle. There are many methods to measure viscosity. Redwood viscosity is commonly used in Britain, Cyberport viscosity is commonly used in the United States, and engler viscosity is commonly used in continental Europe. However, kinematic viscosity is more widely used in various countries because of its higher measurement accuracy, less sample consumption and fast measurement speed. The conversion between various viscosities can usually be approximated by a pre-made conversion table.

At present, 40°C kinematic viscosity (distillate fuel oil) and100 C kinematic viscosity (residual fuel oil) are commonly used in China. In the past, engler viscosity (80 C,100 C) was used as the quality control index in China's fuel oil industry standard, and brands were classified by 80 C kinematic viscosity. The kinematic viscosity of oil is the ratio of dynamic viscosity to density of oil. The unit of kinematic viscosity is Stokes, or Stokes for short. When the dynamic viscosity of the fluid is 1 poise and the density is 1g/cm3, the kinematic viscosity is 1 stokes. CST is the abbreviation of Centistokes, which means Liz, that is, 1 stokes 1%.

sulfur content

Excessive sulfur content in fuel oil will cause corrosion of metal equipment and environmental pollution. According to the sulfur content, fuel oil can be divided into high sulfur, medium sulfur and low sulfur fuel oil. Besides carbon and hydrogen, sulfur is the third main component of petroleum. Although it is much lower than the first two, its content is still an important index. According to the sulfur content, fuel oil is generally divided into low sulfur (LSFO) and high sulfur (HSFO). The sulfur content of the former is below 1%, while the latter usually reaches 3.5% or even 4.5%. There is also low wax oil (LSWR), which has high wax content and high pour point (such as 40 ~ 50℃). High sulfur fuel oil (HSFO) is traded in Shanghai Futures Exchange.

density

It is the ratio of the quality of petroleum products to their volume. Common units-gram/cubic centimeter, kilogram/cubic meter or kilogram/cubic meter, etc. Because volume changes with temperature, density cannot exist independently without temperature. For comparison, the density at15 C is defined as the standard density of western petroleum.

flash(ing) point

It is an indicator of oil security. Petroleum products are heated to a certain temperature under certain standard conditions, so the steam escaping from their surfaces is just enough to form a combustible mixture with the surrounding air. When it comes into contact with the standard test fire source, it will cause instantaneous flash, and the temperature of the oil is defined as its flash point. Its characteristic is that the flame is extinguished instantly, and the oil reaching the flash point temperature cannot provide enough flammable vapor to maintain continuous combustion. Only when it is heated again and reaches another higher temperature, once it encounters a fire source, it will constitute continuous combustion, and the temperature at this time is called ignition point or ignition point. Even so, the flash point is enough to characterize the danger degree of an oil product, and it is customary to classify dangerous goods according to the flash point. Obviously, the lower the flash point, the more dangerous it is, and the higher it is, the safer it is.

moisture

Its existence will affect the freezing point of fuel, and with the increase of water content, the freezing point of fuel will gradually increase. In addition, it will also affect the combustion performance of fuel machinery, which may cause accidents such as flameout and shutdown.

ash

It is the unburned part after combustion, especially after FCC circulating oil and slurry fuel oil, the silicon-aluminum catalyst powder will accelerate the wear of pumps and valves. In addition, ash will cover the heating surface of the boiler and make the heat transfer worse.

mechanical admixture

Mechanical impurities will block the filter screen, resulting in oil pump wear and nozzle blockage, affecting normal combustion.