Boiler fuel oil basic knowledge

Boiler fuel oil basic knowledge

  What is fuel oil

  Most petroleum products can be used as fuel, but fuel oil has different interpretations in different regions. The European concept of fuel oil generally refers to the black viscous residue left over from distillation of crude oil, or its miscibility with lighter components, mainly used as a fuel for steam furnaces and various furnaces or as a large slow Speed diesel fuel and as a variety of industrial fuels. In the United States, however, it refers to any combustible liquid or liquefiable petroleum product with a flash point of at least 37.8°C. It can be either Residual Fuel 011 (also known as Heavy Fuel 011) or distillate fuel oil ( Healing 011). Distillate fuel oil can be obtained not only directly from distilled crude oil (ie, straight-run distillates), but also from other processes such as cracking.

The properties of fuel oil mainly depend on the nature of the crude oil and the processing method. The main specifications that determine the quality of fuel oil include viscosity, sulfur content, and Pour Point, which are used in power plants and other fuel oils. 5. It also regulates vanadium and sodium content.

Natural properties of fuel oil

  Fuel oil is a kind of refined oil and is widely used for power generation in power plants, boiler fuels for ships, fuels for heating furnaces, metallurgical furnaces, and other industrial furnace fuels. The fuel oil is mainly made from cracked residual oil and straight-run residual oil. It is characterized by large viscosity, non-hydrocarbon compounds, gums, and asphaltenes.

(1) Viscosity

  Viscosity is the most important performance index of fuel oil and is the main basis for dividing the grade of fuel oil. It is a measure of the fluid resistance capability, and its size indicates the ease of flow, pumpability, and ease of atomization of the fuel oil. For high-viscosity fuel oils, it is generally required to be preheated to reduce the viscosity to a certain level and then enter the burner so that atomization can be easily sprayed at the nozzle. There are many ways to measure the viscosity. Redwood Viscosity is commonly used in the United Kingdom, Saybolt Viscosity is used in the United States, and Engler Viscosity is often used in continental Europe. However, Kinemetic Viscosity is increasingly used in various countries because of its The accuracy of the measurement is higher than the above methods, and the amount of sample is small and the measurement is rapid. The conversion between various viscosities can usually be approximated by a pre-made conversion table.

At present, the most commonly used in China are 40°C kinematic viscosity (distillate fuel oil) and 100°C kinematic viscosity (residue fuel oil). China's past fuel oil industry standards use the Enzi's viscosity (80 °C, 100 °C) as a quality control index, with 80 °C kinematic viscosity to divide the grade. The kinematic viscosity of an oil is the ratio of the dynamic viscosity and density of the oil. The unit of kinematic viscosity is Stokes, Stokes, or Sn. When the fluid has a kinetic viscosity of 1 poise, the kinematic viscosity at a density of 1 g/cm3 is 1 Stokes. CST is the abbreviation of Centistokes, which means Ces, which is 1 percent of Stokes.

(2) Sulphur content

  Excessive sulfur content in fuel oil can cause corrosion of metal equipment and environmental pollution. According to the level of sulfur, fuel oil can be divided into high sulfur, medium sulfur, low sulfur fuel oil. In addition to carbon and hydrogen, sulfur is the third major component in petroleum components. Although its content is much lower than the former two, its content is still an important indicator. According to the sulfur content, fuel oil generally has low sulfur (LSFO) and high sulfur (HSFO) points, the former containing less than 1% of sulfur, the latter usually up to 3.5% or even 4.5% or more. There is also Low Sulfur Waxy Residual (LSWR), which contains high wax content and high pour point (eg, 40 to 50°C). Trading on the Shanghai Futures Exchange is High-Sulfur Fuel Oil (HSFO).

(3) Density

  It is the ratio of mass to specific product of the oil product. Commonly used units - grams / cubic centimeters, kilograms / cubic meter or male / cubic meters and so on. As the volume changes with temperature, the density cannot separate from the temperature. For comparison purposes, Western regulations set the density at 15°C as the standard density of oil.

(4) Flash point

  Flash point is an indicator of oil safety. The oil is heated to a certain temperature under certain standard conditions, so that the vapor escaping from its surface is just enough to form a flammable mixture with the surrounding air. When a standard test fire source comes into contact with the mixture, it will cause an instantaneous Flash fire, when the temperature of the oil is defined as its flash point. It is characterized by the fact that the flames are immediately extinguished. The oil that reaches the flash point temperature has not yet been able to provide enough flammable vapour to sustain continuous combustion. Only when it is heated again and reaches another higher temperature, once it is in contact with the fire source. The encounter side constitutes continuous combustion, and the temperature at this time is called the ignition point or ignition point (Fire Point or Ignition Point). In spite of this, the flash point is sufficient to characterize the degree of danger of an oil burning fire. It is customary to classify dangerous goods based on the flash point. It is clear that the lower the flash point, the more dangerous it is and the higher the safer it is.

(5) Moisture

  The presence of moisture will affect the freezing point of the fuel oil. As the water content increases, the condensation point of the fuel oil gradually increases. In addition, the moisture will also affect the combustion performance of the fuel machine, which may result in accidents such as flameout and shutdown of the furnace.

(6) Ash

  Ash is the remaining part of the combustion can not burn, especially catalytic cracking cycle oil and oil slurry into the fuel oil, silica-alumina catalyst powder will accelerate the pump, valve wear. In addition, the ash will also cover the heating surface of the boiler, making the heat transfer worse.

(7) Mechanical Impurities

  Mechanical impurities can clog the filter, causing the pump to wear out and the injectors to clog and affect normal combustion.

Classification of fuel oil

  As the last product in the refining process, fuel oil has a strong specificity in product quality control. The final formation of fuel oil products is constrained by many factors such as the type of crude oil, processing technology, and processing depth. According to different standards, fuel oil can be classified as follows:

  (1) According to whether or not a product is formed at the time of shipment, the fuel oil can be classified into a commercial fuel oil and a self-used fuel oil. Commodity fuel oil refers to the fuel oil that forms the commodity in the factory link; the self-use fuel oil refers to the fuel oil that is used in the refinery to produce raw materials or fuel but does not form the commodity in the factory link.

  (2) According to the process flow, fuel oil can be classified into normal pressure heavy oil, decompressed heavy oil, catalytic heavy oil and mixed heavy oil. Atmospheric pressure heavy oil refers to the heavy oil (commonly known as slurry) that is catalyzed by a refinery and fractionated by a cracking device; mixed heavy oil generally refers to a mixture of decompressed heavy oil and catalytic heavy oil.

  (3) According to the application, fuel oil is divided into two major categories: marine engine fuel oil and furnace fuel oil. The former is a mixture of straight-run heavy oil and a certain proportion of diesel, used for large-scale low-speed marine diesel engines (less than 150 rpm). The latter is also known as heavy oil, mainly vacuum residue, or cracked residue or a mixture of both, or heavy oil fuel oil made from suitable cracked light oil for use in various industrial furnaces or boilers as fuel.

     Marine engine fuel oil is a large-scale low-speed diesel fuel oil, its main use performance is that the fuel can be sprayed and atomized well, so that combustion is complete, reduce fuel consumption, reduce carbon deposition and engine wear, thus requiring fuel oil has a certain Viscosity to ensure that the required viscosity (about 21-27 cSt) of the high pressure oil pump and injector can be achieved at preheat temperature, usually more than 38°C. Reye No. 1 has two types of viscosity, 1000 and 1500 seconds. Since the fuel oil must be preheated to reduce the viscosity during use, in order to ensure safe use, the preheat temperature must be about 20°C lower than the flash point of the fuel oil. The flash point of the fuel oil is generally between 70-150°C.

     Heavy oil is mainly used as fuel oil for various boilers and industrial boilers. The working process of various industrial furnace fuel systems is basically the same, that is, the pump sucks the heavy oil from the oil storage tank, removes the mechanical impurities through the coarse and fine separators, and then preheats the preheater to 70-120°C for preheating. After the heavy oil viscosity decreases, and then through the regulator valve at 8-20 days atmospheric pressure, injected into the furnace from the nozzle, the mist of heavy oil mixed with air combustion, combustion exhaust gas discharged into the atmosphere through the chimney.