Introduce several combustion methods of gas boilers

08/23/2021


      The combustion methods of gas boilers and their respective characteristics and scope of application are as follows:

1 ton/2 ton Electric Steam Boiler
            1. Fire chamber combustion: The fuel is sprayed into the furnace with air in powdered (coal), mist (oil), or gaseous (gas) form for suspension combustion, and the equipment becomes a chamber combustion or suspension combustion furnace. The increase in the capacity of the gas boiler is not controlled by the manufacture and layout of the combustion surface. The fuel has a large combustion reaction area and mixes well with air. A smaller excess air coefficient can be used, and the combustion efficiency is higher than that of fire bed combustion. However, because the fuel stays in the furnace for a short time, in order to allow the fuel to burn out, a larger furnace area is required, and fuel adjustment and operation management are easy to realize mechanization and automation. According to the nature of the fuel, there are pulverized coal stoves, oil-fired stoves and gas stoves. The pulverized coal furnace can use solid or liquid slagging, and solid slagging is generally used in the mainland. Liquid slag discharge means that the lower part of the furnace keeps high temperature, the slag is completely melted, and is discharged from the lower part of the furnace in the form of liquid slag, and falls into the granulation water tank through the slag well. In order to maintain the high temperature in the burner area, hot air feeding and high hot air temperature are generally used, which is called an open furnace. There is also a waist in the lower part of the furnace, and the furnace is divided into a slag chamber and a cooling chamber to further increase the temperature of the slag chamber, which is called a semi-open furnace. The furnace temperature decreases as the load decreases. The liquid slag discharge of gas boilers will cause problems such as high temperature corrosion of the water wall, iron precipitation in the slag pool, slag accumulation in the furnace, and high NOx in the exhaust smoke, which need to be paid attention to. Oil and gas furnaces using membrane water-cooled walls are often slightly positive pressure combustion, suitable for low-oxygen combustion, which can reduce the SOx content in the flue gas, reduce low-temperature corrosion, and reduce atmospheric pollution. No induced draft fan is required, only a higher-pressure head blower , The furnace is required to be strictly sealed. The scope of use of gas boiler fire chamber combustion is mainly used in some industrial boilers, and power station boilers generally use this combustion method. The temperature of the burner area of the liquid slagging furnace can reach 1600 degrees Celsius to 1700 degrees Celsius, which is suitable for burning coal with low ash melting point and low volatile coal that is not easy to be fired.


            2. Fire bed combustion: the fuel is layered on the grate, and the air enters the hearth through the fuel layer through the gap of the grate. Most of the fuel is burned in layers on the grate, and a small part of the fine particles and precipitated from the fuel layer Combustible gas burns in the space above the fuel bed, and its equipment becomes a fire bed furnace, a bed furnace or a grate furnace. No milling equipment is needed, the system sees you, but it is controlled by the size of the grate structure. Scope of application: used for industrial boilers and small power station boilers with gas boiler capacity less than or equal to 35.


            3. Cyclone combustion: It is characterized by the fuel flow entering the cyclone tube tangentially or axially, such as fine coal and coarse powder. The high degree of secondary air tangentially enters the cyclone tube to cause a strong swirling airflow, which carries the fuel particles to rotate forward. Most of the large particles are thrown to the slag film on the wall of the tube and burned, and a small part is subdivided into the tube and suspended and burned. The liquid slag Flowing out of the slag opening, the high-temperature flue gas enters the burnout-the cooling furnace is further burned out and cooled. The relative speed of fuel and air is greatly increased, which intensifies combustion. The residence time in the cylinder is prolonged, and the boiler has high thermal efficiency. The cyclone has a small volume and lack of cooling, which is beneficial to maintain high temperature and save steel. It is suitable for a wide range of coals and has a high slag discharge rate. The liquid slag can be made into slag wool or other building materials. The disadvantage is that the structure and manufacturing process are more complicated, the lining maintenance workload is large, the high-pressure blower is required, the fly ash is very fine and easy to deposit, and the NOz is high in severe shots. There are two types of gas boiler cyclone furnaces: vertical and horizontal. The application range of the gas boiler cyclone combustion is already suitable for the comprehensive utilization of fuel calcium magnesium phosphate fertilizer.


            4. Boiling combustion: The air is evenly sent into the furnace through the air distribution plate at an appropriate flow rate to blow up the coal particles and burn them in a boiling (fluidized bed) state on the fire bed. Due to the strong relative movement between the coal particles and the air , And the residence time in the fluidized bed is longer, so the combustion is greatly enhanced. The heating surface (i.e. buried pipe) is often arranged in the fluidized bed, and the ash after combustion flows out from the overflow. For low-quality fuels that cannot be burned in other combustion equipment (such as coal, stone coal, oil shale, etc.), stable fuels can be obtained in a fluidized bed. After solving the problems of wear and efficiency, it is expected to be applied to larger capacity boilers.

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