By Mr.J 2019-10-23 13:15:29
Burners, a traditional industrial machine, have developed with the advancement of society. Develop from a single form to diversification. This has gone through a long period of time. From the initial set of furnaces and ovens, several sets of air and gas openings, to premixed burners, to similar nozzle mixing burners, to date, different types of special burners for different jobs. From the traditional theoretical structure, it is no longer the same. Therefore, it greatly promotes the development of global industry.
Burner improved in theory and practice
For the burner industry, burners have unique characteristic curves, flow ranges and gas-to-air ratios, which are well known. The burner is turned off outside any characteristic curve (conditions). The steady combustion rate is defined by the limit of fuel flammability. For example, the stoichiometric ratio of air to natural gas is about 10:1, but the mixture may burn in the range of 5:1 rich state to 15:1 lean state. These properties are determined by the chemical and physical properties of the gas-air mixture. In addition, if the combustion reaction does not generate enough heat to keep the chain reaction going, the burner will stall.
For the improvement of the internal heat treatment furnace in the early stage of the burner, it is necessary to trace the early oven that uses thin air as fuel. Using a thin air oven, air can be drawn from around the burner, cooling small hot spots and agitating the air in the furnace to make it more uniform; but when the furnace is operating at a higher temperature, the only way to avoid overheating is to periodically shut down. Burner; a problem in a furnace with a composite burner is that it operates at a small ignition rate for a long time, and the temperature in the combustion chamber is extremely uneven, and the burner is extremely hot in front and cold in other places. The limitation for direct-fired furnaces with large combustion chambers is that the fast premixed flames are too short and compact to uniformly project heat in the combustion chamber, so that temperature inconsistencies can occur even at high ignition rates. Therefore, it has been suggested that increasing the burner helps solve this problem. But at the same time, there has been a problem of tempering.
At the beginning of 1920, several single-machine nozzle hybrid burners appeared on the European market. Most of these burners are designed to be very simple. In essence, there are two concentric pipes, one to go air and the other to go gas. The two air streams remain separated until the ignition, so there is no tempering. In addition to this, there is no improvement in the design of such burners and premix burners. Under high fire rate conditions, the flame is not easy to get rid of fire, but the fluctuation of the mixing ratio is still limited. The speed of air and gas must be carefully controlled to ensure a clean and stable flame.
Through on-the-spot investigations on more than 100 domestic and international three-channel pulverized coal burners in the cement industry in China, we learned that the burners using modern latest combustion technology use large speed difference and strong swirl theory to make the flame The internal range of fuel accumulation; reducing the oxygen content in the flame root range and reducing the temperature peak by reducing the primary air consumption; optimizing the burner nozzle system to change the primary air volume by adjusting the nozzle geometry.
The classification of the burner industry abroad is very clear, especially in the United States, where industrial burners and boiler burners have strict boundaries. And this must not be mixed into a pool, used interchangeably.
In the development of the burner, after solving the problem of ignition rate and air-fuel ratio, the burner designers continue to meet the challenge of shaping the flame to adapt to the special process. From the 1920s to the 1950s, many burners with high flame stability, a wide range of ignition rates and air-fuel ratios were produced. By controlling the speed and direction of the gas and air, flames of various shapes can be obtained, from flat type to dish type to long type and fine pencil type. The variety of burners then makes them suitable for a wide range of processes.