I. Concept and Classification of Coal Powder Burners

　　A coal powder burner is a device that enables the complete combustion of coal powder within a short time, generating high-temperature swirling flow. According to their applications, coal powder burners are classified into:

　　1. Rotary kiln coal powder burner;

　　2. Boiler coal powder burner;

　　3. Asphalt mixing plant coal powder burner.

　　II. Introduction to Coal Powder Burners

　　Coal powder burners feature a specially designed multi-stage, multi-nozzle air delivery and guidance structure. They enable coal powder to generate high-temperature swirling flow in a short time, offering complete combustion, high thermal efficiency, smoke and dust removal, energy saving, improved working conditions, and reduced labor intensity. They are ideal energy-saving products.

　　Coal powder combustion technology and low-NOx combustion technology are contradictory technologies. Reducing NOx generation and emissions fundamentally relies on controlling the temperature of the combustion zone to prevent it from becoming too high. However, low-temperature combustion affects the combustion rate of coal powder. The goal is to coordinate the application of these two technologies to achieve a comprehensive effect, which essentially requires controlling the entire coal powder combustion process. This ensures the stability of coal powder ignition, maintains a relatively low combustion temperature, and provides sufficient combustion time at this temperature to ensure complete combustion.

　　III. Technical Basis

　　1. The smoke opacity of the exhaust gas from the coal powder burner is Ringelmann 0-1;

　　2. The fixed carbon content of ash slag in the coal powder burner is around 0.1%, with essentially no carbon powder;

　　3. The energy saving rate of the new coal powder burner is 15-30%;

　　4. With the use of a lower flue in the case where the flue gas content in the burner does not have dust removal equipment, as long as the coal and air combustion is sufficient, national standards can be met.

　　IV. Main Features of Zhongwei Coal Powder Burners

　　1. The residence time of coal powder in the high-temperature zone of the coal powder burner is long, resulting in high combustion efficiency, direct flue gas discharge without black smoke, and steam-like white smoke;

　　2. This type of coal powder burner has a shorter temperature rise time during heating, high thermal efficiency, low coal quality requirements, wide coal type applicability, and high economic efficiency;

　　3. Easy ignition, rapid heating, and significantly improved work efficiency;

　　4. The air volume and coal input of this burner can be changed as needed, and the furnace temperature and flame length can be adjusted within a wide range to meet actual needs;

　　5. The temperature field inside the coal powder burner is uniform, the heated surface area of the body in the furnace is large, the slag does not stick to the surface of the workpiece, and the product quality is good.

　　Zhengzhou Zhongwei Environmental Protection Equipment Co., Ltd. researches and produces two-channel, three-channel, four-channel coal powder burners, and multi-channel coal powder and gas mixed combustion burners.

　　The four-channel coal powder burner is specially designed by Zhongwei Company using foreign technology, targeting different rotary kiln equipment, different coal powder characteristics, and different process conditions. The excellent structural design ensures sufficient mixing of coal powder with primary and secondary air, high combustion efficiency, high thermal intensity, good flame shape, convenient adjustment, and low maintenance costs.

　　V. Applications of Coal Powder Burners

　　Currently, it has been widely used in cement kilns, pelletizing kilns, lime kilns, lithium kilns, magnesium oxide kilns, alumina kilns, chromate kilns, and various types of kilns in the building materials, metallurgy, chemical, and power industries.

　　VI. Structure and Performance Characteristics of MF Series Coal Powder Burners

　　The four-channel coal powder burner consists of: pipelines, nozzles, metal bellows compensators, butterfly valves, pressure measuring instruments, and protective layers.

　　Pipelines: These include the "axial flow duct, swirl flow duct, coal-air duct, central air duct, and fuel oil pipe." Since the fuel oil pipe is for ignition, it is customarily called a four-channel system.

　　Nozzles: Processed from special materials, the different outlet areas of the nozzles in various series of burners are adjustable, thereby adjusting the ejection speed of the air. This is one of the key components that ensures the flame shape and lifespan.

　　Metal bellows compensator: This is the main component for connecting the pipelines, sealing, and adjusting the flame shape.

　　Butterfly valve: Used to adjust the air volume. Pressure measuring instruments: Indirectly display the ejection speed of the air from the nozzle inside the burner.

　　Protective layer: This is the refractory cast layer, which extends the service life of the burner combustion tube.

　　The MF series coal powder burner utilizes the principle of co-flow with a large velocity difference, making full use of secondary air to quickly raise the temperature of the coal powder to its ignition point. A large conical flame is formed immediately after leaving the nozzle. The inner air uses stable plate technology to achieve optimal flame stability, while simultaneously reducing nozzle temperature and extending nozzle lifespan, protecting the kiln skin, and extending the life of the kiln lining. The primary air volume only accounts for 5-7% of the theoretical air volume, resulting in significant energy savings. It can be used for lignite with 30-35% ash content and anthracite with about 10% volatile matter, and NOx emissions can be reduced by 30%.

　　The structure of the four-channel coal powder burner is determined by analyzing various problems encountered in the practical application of three-channel coal powder burners by numerous domestic manufacturers. The nozzle structure of the four-channel coal powder burner is designed from the inside out, with the central air, swirl air, coal air, and direct flow air channels. An ignition oil gun can also be installed in the central air channel according to user requirements. The central air flows out through small holes distributed on the central flame stabilization plate, with a flow rate of about 0.03%-0.05% of the total primary air. Its function is to adjust the negative pressure of the central recirculation zone of the jet and change the position and size of the high-temperature zone at the head.

　　The swirl air channel uses a long helical blade axial swirl generator. Its unique structure not only reduces aerodynamic resistance but also generates sufficient swirl intensity. It is not easily blocked during use, and the use of ceramics on easily worn parts ensures a longer service life. The direct flow air channel is equipped with 12-16 circumferentially distributed nozzles. The special cavity linear design and processing precision of the nozzles ensure that the airflow from the nozzles is strong and powerful, with less energy loss, improving the momentum of the direct flow external air and changing the jet shape.

　　In addition, a flame stabilizer is installed outside the DC wind channel to prevent premature flame dispersion and to protect the nozzle head. Theory and experiments have both proven that a central disc flame stabilizer helps to form an internal recirculation zone. The geometry of the swirl wind outlet has a significant impact on the various velocities in the jet and the location of the internal recirculation zone. Under the same swirl intensity conditions, using an expansion-type extension can increase the radial distance between the axial and tangential velocity peaks and the reverse mass flow.