Volatile matter: It is the primary indicator for determining the ignition characteristics of coal. The higher the volatile content, the easier the ignition and the faster the burning rate. According to the boiler design requirements, the value of the volatile matter of the coal supply should not be too large, otherwise it will affect the normal operation of the boiler. If the original design burns low-volatility coal and burns high-volatility coal, the flame center may approach the burner outlet and may be shut down due to burning of the burner; if the original design burns high-volatility coal The conversion of low-volatility coal will result in incomplete combustion due to too late fire, and even cause a flameout. Therefore, when supplying coal, it should be supplied as much as possible according to the original designed volatile coal or similar coal. Ash: The ash content causes the flame propagation speed to decrease, the ignition time to be delayed, the combustion to be unstable, and the furnace temperature to drop. The higher the ash yield of coal, the lower the calorific value, the lower the combustion temperature, the higher the ash discharge, the lower the thermal efficiency, and the more serious the stain on the heated surface. Therefore, the lower the ash, the better. Moisture: high moisture content, low calorific value, large loss of smoke, and easy to cause blockage of coal bunker, pipeline and coal feeder. However, the presence of moisture has certain advantages. The presence of water vapor in the flame is a very effective catalyst for the suspension combustion of pulverized coal, and the moisture can also prevent the flying of coal dust. Calorific value: Calorific value is an important basis for boiler design. Since the coal powder of the power plant has strong adaptability to the coal type, as long as the calorific value of the coal is substantially consistent with the boiler design requirements, it is generally not lower than the design value of 0.8 MJ/Kg. Coal ash fusibility: ST ≥ 1350 ° C for solid waste slag pulverized coal furnace. Below this temperature, it may cause slagging in the furnace and hinder the normal operation of the boiler. The liquid slag pulverized coal furnace requires that the lower the ash fusibility, the better, and the lower the ash viscosity is, the better. (Gray melting point: Since the flame center temperature of the pulverized coal hearth furnace is more than 1500 °C, the coal ash is mostly softened or fluidized at such high temperature.) Sulfur content of coal: Sulfur is a harmful impurity in coal. Although it has no effect on the combustion itself, its content is too high, and the corrosion of equipment and environmental pollution are quite serious. Therefore, the sulfur content of coal-fired power plants should not be too high, generally the maximum requirement should not exceed 2.5%. High-sulfur coal is easy to self-ignite when stored in coal bunkers, so the lower the sulfur content, the better, wd(St)<1.25pc. the best. Particle size: The suspension furnace burns coal powder. The finer the coal powder, the easier it is to catch fire and burn completely, the heat loss is small, but the power consumption increases, and the flying loss is large. Generally, the particle size is 0 to 30 mm, and most of the 20 to 50 um particle size is uniform. China stipulates that the particle size requirements for coal used in coal-fired boilers for thermal power plants (washing) should be 13mm, (mixed) mixed coal <25mm, medium coal, washed coal <50mm, if the above coal supply is insufficient, it can be temporarily For raw coal. Quality requirements for power generation coal for power plants: The quality of coal used in thermal power plants is an important basis for boiler design and production processes. The characteristics of fuel coal include two aspects: one is coal characteristics, and the other is ash characteristics. Coal characteristics refer to coal moisture, ash, volatile matter, fixed carbon, element content (carbon, hydrogen, oxygen, nitrogen, sulfur), calorific value, ignition temperature, grindability, particle size and the like. These indicators are directly related to combustion, processing (eg grinding into coal), transport and storage. The ash property refers to the chemical composition of the coal ash, the characteristics at high temperatures, and the specific resistance. These characteristics have a great influence on the degree of cleanliness after combustion, the corrosiveness of steel, and the removal of coal ash. The power plant pulverized coal furnace has a wide application range to coal types. It can be designed to burn high-volatility lignite or to design low-volatility anthracite. However, for a boiler that has been installed and used, it is impossible to burn coal with various volatiles because it is limited by the type of burner and the structure of the furnace. 2,2`-Azobisisobutyronitrile,2 2 -Azobisisobutyronitrile Cas 78-67-1,Aibn Used As Rubber Plastic,Aibn Used As Polymerization Initiator SHANDONG MINGDE CHEMICAL CO.,LTD. , https://www.sdmingdechem.com
Coal quality indicators and requirements for power generation in power plants
1. The power plants use coal quality indicators: